THE  LIBRARY 

OF 

THE  UNIVERSITY 

OF  CALIFORNIA 

LOS  ANGELES 


GIFT  OF 

John  S.Prell 


m- 


^Si 


€«ti: 


& 


SEWERAGE   MAP 

—  OF  THE  — 

VILLAGE  OF 

WEST  TROY 

NEW    YORK. 

CADY    STAjLEY.    Engineer 
■.  d.  PIERSON.  ConstTQCtiag  Engine 


1555 


T     BXFLA.NA 


C0MMIS5I0NEB5. 

Peter  A.  Rogers.  Pies. 
Terraace  Cummings. 
Jajn.es  C.  Covert. 

1  T.  VanVranken. 
James  H.  Harmon. 
Alfred  Mosber. 
William  Andrews. 
Ificbolas   T.  Kane. 


THE 


SEPARATE  SYSTEM 

OF  SEWERAGE, 

ITS  THEORY  AND  CONSTRUCTION, 


BY 

CADY   STALEY, 

PRESIDENT    OF    CASE   SCHOOL   OF    APPLIED   SCIENCE,    CLEVELAND,    O. 
AND 

GEO.   S.   PIERSON, 

MEMBERS    OF    THE   AMERICAN    SOCIETY    OF    CIVIL    ENGINEERS. 


THIRD    EDITION, 
REVISED    AND    ENLARGED, 

With  a  Chapter  of  Sewage  Disposal. 

JOHfl  S,  PRELL 

Civil  &  Mechanical  Engineer, 

SAN  FS^^QlSefi,  CAL. 

D.   VAN    NOSTRAND,    CO., 

23  Murray  and  27  Warren  Streets, 
1899. 


Copyright,  i886,  by  GEO.  S.    PIERSON. 


Copyright,  1891,  by  GEO.  S.  PIERSON. 


Copyright,  1899,  by  GEO.  S.  PIERSON. 


From  the  Press  of 

Ihling  Bros.  &  Everard, 

Kalamazoo,  Mich. 


Eaginecriif 
Lifcraij 

PREFACE  TO  THE  THIRD  EDITION. 


The  second  edition  of  this  book  was  exhausted  about  a 
year  ag^o.  The  greater  part  of  the  book  has  been  re-written. 
Statistical  tables  have  been  revised  and  new  matter,  includ- 
ing- many  plates  and  diag^rams,  has  been  added.  Old  matter 
that  is  now  of  doubtful  value  has  been  eliminated. 


PREFACE  TO  THE  SECOND  EDITION. 


The  first  edition  of  this  book  was  exhausted  some  time 
since  and  numerous  calls  have  been  made  for  another 
edition.  The  book  has  been  entirely  re-written  and  much 
new  matter  has  been  added.  An  effort  has  been  made  to 
facilitate  computations  by  Kutter's  formula  and  tables  of  the 
value  of  ;/  have  been  added  to  assist  in  a  proper  determina- 
tion of  its  value  for  sewers. 

The  question  of  Sewag^e  Disposal  has  also  received 
attention. 


733285 


PREFACE  TO  THE  FIRST  EDITION. 


The  subject  of  the  sewerag'e  of  towns  is  attracting" 
much  more  attention  now  than  formerly.  The  reason  for 
this  is  evident.  While  the  country  was  new  and  the  towns 
small  and  sparsely  built,  the  disposal  of  the  liquid  wastes 
and  other  refuse  was  left  to  be  provided  for  by  each  house- 
holder as  he  might  deem  best. 

Various  plans  were  employed,  most  of  which  were 
objectionable,  and,  in  many  cases,  no  plan  at  all.  But  as  the 
towns  increase  in  size  and  are  more  compactly  built  the 
question  of  a  proper  system  of  Sewerage  forces  itself  upon 
the  attention  of  the  people.  Some  general  system  must  be 
adopted  for  the  whole  town  and  the  question  is,  what 
system? 

The  moderate  cost  of  the  "Separate  System"  makes  it 
possible  to  carry  out  a  system  of  sewerage  in  many  cases 
where  the  expense  of  the  "Combined  System"  would  make 
the  construction  of  sewers  impossible. 

One  hindrance  to  the  rapid  introduction  of  the  Separate 
System  has  been  the  lack  of  available  information  concerning" 
it.  Much  has  been  written  on  the  subject,  but  the  neces- 
sary information  is  scattered  in  numerous  pamphlets, 
reports  and  papers  presented  to  scientific  societies  in  the 
United  States  and  in  England. 

The  object  of  this  book  is  to  explain  what  the  Separate 


Vlll  PREFACE    TO    THE    FIRST    EDITION. 

System  is,  what  it  is  designed  to  do,  and  to  g"ive  practical 
directions  for  designing"  and  constructing  sewers  in  accord- 
ance with  that  system. 

No  single  design,  however  complete  in  all  its  details,  will 
be  best  adapted  to  every  case.  Each  town  will  present  some 
features  peculiar  to  itself  and  the  general  plan  must  be 
modified  to  suit  the  conditions  of  each  case.  All  that  is  here 
attempted  is  to  give  sufficient  theory,  data  and  results  of 
experience  to  guide  in  properly  designing  and  constructing 
sewers  on  the  Separate  System. 


CONTENTS. 

CHAPTER  I. 

INTRODUCTION.^ — PAGK    17. 

Need  of  Sewerag^e. — Pollution  of  Streams. — Pollution  of  the 
Subsoil  and  Wells. — Typhoid  Fever. — Analysis  of  Well 
Water. — Effect  of  Sewerag'e. — Systems  in  Use. 

CHAPTER  n. 

WATER    CARRIAGE    SYSTEMS. — PAGE    39. 

The  Combined  System. — The  Separate  System. — Subsoil 
Drainag"e. 

CHAPTER  m. 

THE    SEPARATE    SYSTEM. PAGE    46. 

Roof  Water.- — Size  and  Material. — Flushing-. — Ventilation. — 
Special  Features. — Adaptability  of  the  Separate  System. 

CHAPTER  IV. 

PLANS. — PAGE    58. 

Sewag-e  Disposal. — Storm  Water. — The  Preliminary  Survey. 
— Capacity  Required. — Chang-es  of  Temperature. — Use 
of  Water  Increasing*. 

CHAPTER  V. 

QUANTITY    OF    SEWAGE. PAGE    66. 

The  Quantity  of  Water  Required. — Varying-  Rates  of  Water 
Consumption. — Statistics  of  Water  Consumption. — 
Sewer  Gaug-ings. — Subsoil  Water. 


CONTENTS. 


CHAPTER  VI. 

LAWS    OF    FLOW    IN    SEWERS. — PAGE    94. 

Effect  of  Increasing- Size. — Effect  of  Hydraulic  Mean  Radius. 
■ — Computation  of  Discharg-e  and  Velocity  for  any  Diam- 
eter and  any  Depth  of  Flow. — Velocity  Required  to 
Prevent  Deposit. — Effect  of  Decreasing-  Quantity  of 
Sewag-e.  —  Minimum  Velocity. — Graphical  Solution. — 
Comparison  of  Various  Standard  Formulae. — Loss  of 
Head  on  Curves. — Empirical  Formula. 

CHAPTER  VII. 

MATERIAL    AND    ACCESSORIES. — PAGE    130. 

Sewer  Pipes. — Hand-Holes. — Lamp-Holes. — Fresh  Air  In- 
lets.— Man-Holes. — Flush-Tanks. — Y  Branches. 

CHAPTER  VIII. 

SPECIFICATIONS    AND    CONTRACT. — PAGE    138. 

Letting-  the  Contract. — Form  for  Advertisement. — Instruct- 
ions to  Contractors. — Form  of  Proposal. — Form  for 
Specifications  and  Contract. — Form  of  Bond. 

CHAPTER  IX. 

CONSTRUCTION. — PAGE    158. 

Importance  of  Record. — Alig-nment. — Reference  Points. — 
Methods  of  Work. — Curves. — Transit  Notes.  ^ — Level 
Notes. — Profiles. — Working-  Map. — Note  Books. — Con- 
struction.— Pipe  Laying-. — Depth. — Grade  Line. — Brac- 
ing- and  Sheet  Piling-. — Inspection  of  Material. — Location 
of  Y  Branches. — Artificial  Foundation. — Man-Holes. — 
Flush-Tanks. — Lamp-Holes. — Outlets. — House-Sewers. 
— Pumping-  Stations. 


CONTENTS.  XI 


CHAPTER  X. 

FLUSHING    AND    VKNTILATING PAGE    200. 

In  the  Combined  System. — In  the  Separate  System. — Roof 
Water.  —  Traps  on  Main  Drain. — Automatic  Flush- 
Tanks. —  Field-Waring-  Flush-Tank. — Van  Vranken's 
Flush-Tank.  — The  Miller  Automatic  Flush-Tank.— 
Rhoads-Williams  Flush-Tank. — The  Lig-htning-  Auto- 
matic Flush-Tank.  —  Valve  Tanks. — Requirements  to 
be  met. — Quantity  of  Water  Required. — Rapidity  of 
Discharg-e. — Experimental  Data. — General  Statements. 

CHAPTER  XL 

HOUSE    DRAINAGE    AND    PLUMBING. — PAGE    240. 

House  Connections. — Municipal  Control. — Form  of  Ordinance 
and  Rules  for  Plumbing-. — Form  of  License. — Form  of 
Bond. — Form  of  Application. — Form  of  Permit. — House 
Drains,  th«  Subsoil. — House  Sewers. — Grease  Traps. — 
Soil  and  Waste  Pipes. — Traps  and  Ventilation. — General 
Features. 

CHAPTER  XIL 

COST    AND    ASSESSMENTS. PAGE    268. 

Comparative  Cost  of  the  Separate  and  Combined  Systems. — 
Cost  of  the  Separate  System. — Examples  of  Cost  from 
Actual  Work. — Data  and  Cost  of  Various  Systems. — 
Examples  of  Cost  Computed  from  Time  Book.— Cost  of 
Maintenance. — Sewer  Assessments. — Assessments  Dis- 
tributed over  a  Series  of  Years. — Installment  Table. 

CHAPTER  XIII. 

COMBINED   SEWERS. — PAGE    292. 

Formula?.— Form  of  Sewers.— Materials.— Catch  Basins. — 
Man-Holes. 


XII  CONTENTS. 


CHAPTER  XIV. 

SEWAGE    DISPOSAL. — PAGE    296. 

Dilution. — Subsidence. — Filtration.  — Chemical  Processes. — 
Application  to  the  Soil. 

CHAPTER  XV. 

PURIFICATION    OF    SEWAGE    BY    APPLICATION    TO    THE    SOIL. 

PAGE    299. 

General  Considerations. — The  Influence  of  the  Bacteria  of 
Nitrification.- — Nitrification. — Absorptive  Power  of  the 
Soil. — The  Function  of  Nitrates  in  Plant  Life. — Experi- 
ments of  the  Massachusetts  State  Board  of  Health. — 
The  Influence  of  Temperature. — Aeration  of  the  Soil. — 
Effect  of  Different  Soils. — Self  Purification  of  the  Soil. — 
Quantity  and  Concentration  of  Sewag"e. — Influence  of 
Area. — Sewag^e  Disposal  at  Pullman. 


LIST  OF  ILLUSTRATIONS. 

Page. 

Sewerag-e  Map,  West  Troy,  N.  Y 

Shone  Ejector 36 

Diag-ram  of  Sewer  Gaug-ing-s  at  St.  Louis 87 

Weir  for  Measuring  Flow 90 

Observation  Opening,  etc 97 

Diagram   Showing    Comparative    Velocity   and   Dis- 
charge in  Circular  Sewers  of  a  Given  Diameter 

and  Grade  for  Various  Depths  of  Flow 100 

Graphical  Sewer  Calculations 108 

Hand-Hole 133 

Details  of  Fresh  Air  Inlet 135 

Sketch  of  Construction — Photo.  Engraving 167 

Details  of  Sheet  Piling 170 

Cradle 172 

Details  of  Man-Hole 173-4-5-9 

Cast-iron  Head  and  Dust  Pan 181 

Iron  Cover,  Man-Hole  and  Flush  Tank 183 

Outlet  Chamber 185 

Outlet  Chamber  with  Relief  Overflow 186 

Submerged  Iron  Outlet,  Dayton,  Ohio 187-9 

Photograph  of  Junction  During  Construction 191 

Man-Hole— Brick  Sewer 193 

Pumping  Plant 196 

Branches,  Curves  and  House  Drains 197 

Main  Traps  and  Air  Inlets 207 

Main  Traps  and  Air  Inlets 211 

Field-Waring  Flush-Tank 216 

Van  Vranken  Flush-Tank 218 

Miller  Flush-Tank 221-3 

Rhoads-Williams  Flush-Tank 226 

The  Lightning  Automatic  Flush-Tank 227 

Flush- Wave 235-8 

Interior  Plumbing 255 

Sewage  Filter  Beds  at  Pullman — Photo.  Engraving..  321 

Broad  Irrigation  Area  at  Pullman — Photo.  Engraving  323 


LIST  OF  TABLES. 


Table  No.  Page. 

I.     Urban  Population  of  the  United  States 55 

II.     Cities  Classified  According-  to  Population. .  .        56 

III.  Actual  Consumption  by  Meter TO 

IV.  Showing-  Consumption  of  Water  in  Twelve 

American  Cities  in  1874  and  1884 72 

V.     Showing-  Per  Diem  Per  Capita  Consumption 
of  Water  in  One  Hundred  and  Seventy-Six 

American  Cities  in  1884 73 

VI.     Illustrating-  Monthly  Variation  in  the  Con- 
sumption of  Water 74 

VII.     Illustrating-    Extreme   Daily    Variations    in 

Consumption  of  Water 75 

VIII.     Hourh' Variations  in  Water  Consumption.. .        76 
IX.     Showing-  Rates  of  Water  Consumption   for 

Different  Periods  of  Twenty-Four  Hours       77 

X.     Water  Consumption  at  Louisville,  Kv 79 

XI.     Sewer  Gaug-ing-s  at  St.  Louis 81 

XII.     Comparison  of  Sewer  Gaug-ing-s 84 

XIII.  Gaug-ing-s  of  Water  Street  Main  Sewer,  Kal- 

amazoo, Mich 89 

XIV.  Illustrating-  Effect  of  Increased  Section,  the 

VolumeofDischarg-e  Remaining- the  Same       95 
XV.     Showing-    the    Comparative    Discharg-e    and 
Velocity  in  Circular  Sewers  of  a  Given 
Diameter  and  Grade  for  A^arious  Depths 

of  Flow 99 

XVI.     Minimum  Velocities  and  Grades  in  Circular 

Sewers 105 

XVII.     Showing-  Maximum  Rate  of  Sewag-e  Flow.  . .      109 
XVIIL     Values  of  //,  Kutter's  Formula 112 


XVI 


LIST    OF    TABLES. 


XIX.  Comparing-  the  Discharg-e  in  Various  Cases 

as  Given  by  Different  Standard  Formulae  125 
XX.  Showing-    Increased     Frictional     Head     Re- 
quired for  Curves  in  Various  Cases 128 

XXL  Tests  of  Sewer  Pipe 131 

XXII.  Park  Street  Sewer 232 

XXIII.  Connecticut  Avenue  Sewer 233 

XXIV.  Chapin  Street  Sewer 234 

XXV.  Thirty-Second  Street  Sewer 234 

XXVI.  House  Drains 254 

XXVII.  Bids  on  Sewer  Construction,   Schenectady, 

N.  Y '..  267 

XXVIII.  Bids  on  Sewer  Construction,  West  Troy,N.Y.  269 

XXIX.  Bids  on  Sewer  Construction,  Dayton,  Ohio. .  273 

XXX.  Cost  of  Thirty-Five  Sewerage  Systems 276 

XXXI.  Actual  Cost  of  Labor  and  Material 278 

XXXII.  Actual  Cost  of  Labor  and  Material 279 

XXXIII.  Actual  Cost  of  Labor  and  Material 280 

XXXIV.  Actual  Cost  of  Labor  and  Material 280 

XXXV.  Cost  of  Sewers  in  Chicago,  1890 281 

XXXVI.  Installment  Table 289 


The  Separate  System  of  Sewerage. 


CHAPTER  I. 

INTRODUCTION. 

"Sanitar}^  Eng-ineerin^"  has  been  defined  as  that  branch 
of  eng'ineerinw'  which  has  for  its  object  the  improvement  of 
the  health  of  towns  and  districts,  by  bring-ing-  to  them  a  sup- 
ply of  those  thing's  which  promote  health,  and  carrying-  from 
them  those  thing-s  which  are  injurious  to  it. 

The  three  principal  requirements  for  the  promotion  of 
health  are  wholesome  food,  pure  water,  and  pure  air.  An 
abundant  and  cheap  supply  of  food  is  best  secured  by  per- 
fecting- the  means  of  transportation  by  land  and  water. 
Pure  water  may  be  supplied  by  suitable  water  works.  The 
air  is  kept  pure  by  removing-  from  the  districts  those  thing-s 
which  pollute  it:  that  is,  by  removing-  all  g-arbag-e,  and  by 
carrying-  out  a  proper  system  of  drainag-e  and  sewerag-e. 

Although  all  of  these  works  contribute  to  the  health  of  a 
district,  3'et  the  subdivision  of  labor  in  these  times  has 
increased  the  number  of  specialties  in  the  eng-ineering-  pro- 
fession and  has  limited  the  field  of  the  Sanitar}^  Eng-ineer. 
By  common  consent  the  eng-ineer  who  plans  and  executes 
works  for  improving  the  means  for  transportation  is  called  a 
Civil  Engineer;  the  eng-ineer  of  a  system  of  water  works  is 
called  a  H)'draulic  Eng-ineer;  leaving-  the  Sanitarj^  Eng-ineer 
the  task  of  removing-  from  any  locality  whatever  may  be  det- 
rimental to  health;  thus  assig-ning-  to  him  the  roll  of  scien- 
tific scaveng-er. 


18  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

Man  himself  is  the  principal  cause  of  the  defilement  of 
his  surrounding's.  His  presence  bring-s  pollution  to  earth, 
air  and  water.  Nature  provides  a  remedy  which  is  efficient 
only  to  a  limited  extent.  Refuse  from  the  animal  king-dom  is 
food  for  the  veg-etable  king-dom.  But  when  human  being-s 
cong-regfate  in  masses  nature  can  no  long^er  meet  the 
demands. 

In  country  districts,  where  the  population  is  sparse,  the 
disposal  of  excrementitious  and  refuse  matter  is  easily  man- 
ag-ed  by  each  householder  in  his  own  way.  And  even  if  that 
way  be  unadvisable  the  only  sufferers  are  himself  and  those 
of  his  own  household,  and  no  one  else  will  care  to  interfere. 
The  methods  usually  there  adopted,  however,  become  very 
objectionable  wherever  the  people  cong-reg"ate  in  larg-e  num- 
bers. The  conditions  of  living-  become  chang-ed.  The  sani- 
tary condition  of  the  immediate  surrounding's  of  each  indi- 
vidual concerns  not  only  himself,  but  the  whole  community 
in  which  he  lives;  and  what  was  before  a  personal  matter 
now  becomes  a  question  of  public  policy. 

In  all  densely  populated  areas,  as  in  larg-e  villag-es  and 
cities,  the  disposal  of  the  solid  and  liquid  refuse  becomes  a 
serious  problem.  The  Mosaic  reg-ulations  (Deut.  xxiii,  12- 
13)  can  not  be  enforced,  and  to  store  the  filth  of  a  city  within 
the  city  is  simply  to  invite  disease  and  death. 

The  use  of  the  pits,  dug-  in  the  earth,  as  receptacles  for 
refuse,  is  in  every  way  objectionable.  The  soil  becomes  pol- 
luted with  sewag-e,  and  the  air  is  filled  with  the  noxious  g-ases 
arising-  from  the  sewag-e  soaked  earth,  and  from  the  putrefy- 
ing- masses  in  vaults  and  cess-pools.  The  decomposition  of 
so  much  refuse  in  such  close  proximity  to  the  dwelling-s  is 
detrimental  to  health  in  two  ways.  It  uses  up  the  oxyg-en 
from  the  air,  and  loads  it  with  pestilential  g-ases.  If  cess- 
pools are  used  at  all,  they  should  be  water  tig-ht.  This 
necessitates   the   constantly   recurring-  trouble  of  carrying- 


CHAP.  I.  INTRODUCTION.  19 

away  the  contents  when  they  fill  up,  and  only  parti \'  remov^es 
the  difficulty. 

Need  of  Sewerage — An  examination  into  the  sanitary 
condition  of  a  majority  of  our  older  cities  and  villag^es  will 
show  the  g"reat  need  of  some  kind  of  sewerage.  Many  of 
them  have  never  taken  any  measures  to  rid  themselves  of  the 
necessary  accumulations  of  filth,  incident  to  a  considerable 
population.  For  g^eneration  after  g^eneration  the  refuse 
which  should  have  been  removed  far  from  the  dwelling's,  has 
been  flung  upon  the  surface  of  the  g-round  or  into  cess-pools, 
where  the  putrefying-  mass  poisons  the  air,  and  appeals  in 
more  ways  than  one  for  a  remedy.  "The  offense,  is  rank." 
On  one  of  the  principal  streets  in  one  of  our  oldest  cities  it 
became  necessar}-  to  remove  several  small  houses  to  erect  a 
larg-e  building-.  The  interior  of  the  block  was  thus  exposed 
to  view,  and  it  simply  made  apparent  the  state  of  affairs  in 
nearly  every  block  in  the  city.  Within  the  space  of  150  feet 
long-  by  50  feet  wide,  there  were  four  wells  and  seven  vaults 
and  cess-pools.  It  needs  no  chemical  analysis  to  determine 
the  impurity  of  water  obtained  under  such  circumstances, 
nor  a  very  vivid  imag-ination  to  conceive  the  foulness  of  the 
atmosphere  in  that  locality. 

The  earth  upon  which  many  of  our  cities  stand  is  liter- 
ally saturated  with  sewag-e.  The  vile  odors  which  are 
exhaled  from  the  polluted  soil,  and  from  the  sinks  of  rotten- 
ness and  putrefaction  which  it  contains,  contaminate  the  air 
in  the  streets,  and  are  a  constant  reminder  of  the  need  of  an 
efficient  remedy.  There  they  stand,  j-eeking-  in  the  accum- 
ulated filth  of  past  g-enerations,  never  for  a  day  free  from 
malaria,  and  zymotic  diseases;  and  yet  the  remedy  is  easih^ 
applied  and  the  cost  of  it  within  the  reach  of  the  poorest 
hamlet. 

Pollution  of  Streams. — A  small  water  course  running- 
throug-h  a  city  without  sewers  is  sure  to  become  a  nuisance. 
Ever}'  conceivable  variety  of  filth  and  refuse  will  be  thrown 


20  THB    SEPARATE    SYSTEM    OF    SEWERAGE. 

into  it,  and  it  will  soon  be  simply  an  open  sewer.  In  dry 
weather,  when  the  flow  of  water  is  at  its  minimum,  the  bed  of 
the  stream  will  become  an  elong"ated,  open  cess-pool  of  the 
worst  variety.  The  channel  is  sometimes  cleared  by  throw- 
ing" the  accumulations  of  filth  upon  the  banks:  that  is,  the 
filth  is  spread  over  alarg-er  surface  instead  of  being-  removed. 
Periodical  cleanings  of  the  bed  and  banks  of  the  stream  will 
only  mitig-ate  the  nuisance  temporarily.  The  cure  must 
reach  the  cause  of  the  evil  if  it  is  to  be  radical  and  entire. 
The  sewage  must  be  provided  for  in  proper  channels  of  its 
own,  and  only  the  storm  water  be  allowed  to  run  into  the 
open  water  courses. 

The  following  extracts  are  taken  from  a  report  of  the 
State  Board  of  Health  of  New  York.  The  name  of  the  city 
referred  to  is  omitted,  but  the  name  of  any  unsewered  city 
or  village  might  be  filled  into  the  blank  spaces  and  the  report 
would  give  the  actual  sanitary  condition  in  a  majority  of 
cases: 

"  Dr.  Carroll's  full  report  on  the  prevalence  of  filth  and  malarial  diseases 

in ,  and  the  causes  thereof,  is  well  worthy  a  careful  reading  by  every 

citizen  of . 

"  The  record  is  both  sad  and  alarming.  Sad,  because  it  shows  that  at  least 
one-fifth  of  the  deaths  in  your  city  during  the  past  year  were  clearly  preventable 
by  ordinary  municipal  provision  for  cleanliness;  alarming,  because  the  already 
abnormal  death  rate  from  filth  poisoning  must,  from  the  very  nature  of  the 
cause,  steadily  increase. affords  another  of  the  many  lamentable  illus- 
trations of  the  apparently  ineradicable  popular  delusions  that  natural  water 
courses  are  the  proper  receptacles  for  sewage  and  house  refuse  of  all  kinds. 
*  *  It  appears  from  the  report  that  the  number  of  fatal  cases  from  diphthe- 
ria, typhoid  fever,  diarrhoea*and  scarlet  fever  is,  at  least,  three  times  as  great 
as  it  should  be  under  normal  sanitary  conditions.  These  diseases  are  known  to 
be  intensified,  if  not  directly  caused,  by  filth  poisoning.  The  prevalence  of 
malarial  diseases  is  also  reported.     *     *     *     There  seems  to  be  no  doubt  that 

there  is  a  large  amount  of  malarial  trouble  in .     This  disease  is  usually 

associated  with  surface  or  sub-soil  saturation,  occurring  either  immediately 
around  dwellings  or  within  such  a  distance  that  miasmatic  emanations  may  be 
carried  by  the  winds  over  an  inhabited  locality.  There  appear  therefore,  to  be 
at  least  two  prominent  classes  of  more  or  less  preventable  diseases  occurring  in 


CHAP.  I.  INTRODUCTION.  21 

,   one  of  them  dependent  upon  conditions  of  filth  and   the  other  upon 

undrained  or  saturated  lands.     The  nature  of  these  two  classes  leads   to  the 

conclusion,    that  filth  is  accumulating  within  the  city  of in  such  a  way, 

and  in  such  places,  as  to  affect  the  public  health,  and  that  there  are  saturated 
tracts  which  produce  malarial  diseases. 

"The  first  and  most  important  measure  to  stop  the  present  death  rate  from 

filth  diseases  in is  to  provide  proper  means  of  carrying  away  the  organic 

filth  of  the  city.  The  use  of  open  brook  channels  as  sewers  should  be  abso- 
lutely prohibited.  They  should  be  reserved  for  the  drainage  of  surface  water 
only.  Such  a  prohibition  can  hardly  be  made  effectual  until  some  means  are 
provided  for  carrying  the  sewage  away  from  the  city.  For  this  purpose  a 
system  of  sewers  is  strongly  advised,  and  little  relief  can  be  expected  from  the 
present  unwholesome  condition  of  the  city  until  sewers  have  been  built.     *     *" 

Pollution  of  the  Subsoil  and  of  Wells. — The  ordinary 
cess-pools  are  especially  objectionable  where  wells  are  used 
as  a  source  of  water  supply.  A  well  is  simply  a  hole  dug-  in 
the  g-round,  into  which  the  water,  which  has  sunk  into  the 
earth,  may  drain.  The  quality  of  the  water  will  depend  upon 
the  condition  of  the  soil  through  which  it  passes.  In  cities 
without  sewerage,  cess-pools  by  hundreds  are  formed  in  the 
earth,  into  which  all  manner  of  filth  is  thrown.  Into  this 
same  soil  wells  are  dug,  and  the  drippings  from  the  cess- 
pools are  caught  and  drank,  and  the  seeds  of  disease  are 
sown  broadcast  in  the  community.  One  often  hears  it  said 
that  water  which  passes  through  the  earth  is  filtered  and 
purified.  But  it  must  not  be  forgotten  that  while  the  earth 
acts  as  a  sieve,  and  removes  the  suspended  impurities  the 
oxydation  and  nitrifaction  of  organic  matter  depends  upon 
circumstances  which  are  not  likely  to  be  favorable  very  far 
beneath  the  surface  of  the  ground.  Whatever  is  in  solution 
remains,  to  a  larg-e  extent,  in  the  water. 

The  Swiss  village  of  Lausen,  near  Basle,  is  supplied  with 
w'ater  from  a  spring,  situated  at  the  foot  of  a  mountainous 
ridge,  called  the  Stockhalden.  In  this  village,  where  there 
had  not  been  a  sing-le  case  of  fever  in  many  years,  an  epidemic 
of  typhoid  fever  broke  out,  which  struck  down  seventeen  per 
cent,    of   the   whole   population.      The   cases   of   fever   were 


22  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

pretty  evenly  distributed  among"  the  families  in  the  village, 
with  the  exception  of  six.  As  the  six  families  which  escaped 
did  not  use  water  from  the  spring-,  suspicions  were  aroused 
concerning-  the  water  and  investigations  were  made.  It  had 
previously  been  noticed  that  when  the  meadows  in  the  Fur- 
lerthal — a  little  valley  on  the  other  side  of  the  Stockhalden 
ridge — were  irrig-ated,  the  volume  of  water  in  the  spring  was 
increased;  and  by  the  sinking  of  the  soil  in  one  of  the 
meadows  in  the  Furlerthal,  a  vein  of  water  was  discovered, 
which,  it  was  supposed,  led  to  the  spring  in  Lausen.  It  was 
found,  upon  investigation,  that  a  peasant  living  in  the  Fur- 
lerthal had  returned  home  from  a  distant  city,  sick  with 
fever,  and  that  the  brook  in  which  his  clothes  had  been 
washed  and  into  which  the  slops  from  the  house  had  been 
thrown,  had  been  used  to  irrigate  the  meadows.  This  water 
thus  spread  out  over  the  fields  and  then  filtered  through  the 
ridge,  a  distance  of  a  mile,  still  carried  the  germs  of  disease 
in  it,  and  brought  death  to  the  unsuspecting  inhabitants  of 
Lausen. 

To  prove,  conclusively,  that  the  spring  was  supplied  from 
the  Furlerthal,  and  to  determine  whether  the  water  passed 
through  an  open  vein  or  was  filtered  through  porous  material, 
the  following  experiments  were  made:  Several  hundred 
weight  of  salt  was  dissolved  and  poured  into  the  hole  in  the 
Furlerthal,  where  the  vein  was  discovered.  In  a  few  hours 
the  water  of  the  spring  became  very  salt,  and  the  connection 
between  the  water  in  the  Furlerthal  and  the  spring-  at  Lausen 
was  established  beyond  a  doubt. 

Thev  now  mixed  two  and  a  half  tons  of  flour  in  water 
and  poured  it  into  the  hole,  but  no  trace  of  the  flour  could  be 
found  in  the  spring,  proving  that  the  water  was  so  thoroughly 
filtered  as  to  remove  the  minutest  particles  of  the  flour,  and 
yet  it  still  retained  its  infective  properties. 

Clearness  is  no  proof  of  purity  in  water.  The  water  of 
the  Saratoga  Springs,  although  thoroughly  impregnated  with 


CHAP.    I.  INTRODUCTION.  23 

various  minerals,  are  as  clear  as  ordinary  spring  water,  and 
in  a  g-lass  of  water  as  clear  as  crystal  there  may  be  poison 
enoug-h  to  kill  a  whole  family;  not  only  by  the  comparatively 
slow  and  uncertain  process  of  fever,  but  surely  and  immedi- 
ately. Deleterious  g^ases  may  indeed  add  a  sparkle  to  well 
water,  and  the  peculiar  flavor  so  hig-hly  prized  in  some  wells 
may  be  borrowed  from  a  neig-hboring-  cess-pool. 

Dr.  Victor  C.  Vaug-hn,  Professor  of  Physiolog-ical  and 
Pathologfical  chemistry  in  Michig-an  University,  states  in  a 
report  to  the  State  Board  of  Health,  that  a  series  of  experi- 
ments which  he  has  conducted  confirms  the  g-erm  theory  in 
cases  of  typhoid  fever.  The  fever  was  produced  in  a  cat  by 
inoculation  and  the  cat  showed  all  the  symptomsof  the  disease. 
In  connection  with  this  Dr.  Vaug^hn  states: 

"Last  August  there  was  an  epidemic  of  typhoid  fever  in  the  village  of  Iron 
Mountain,  a  place  in  Northern  Michigan  of  about  4,000  inhabitants.  Part  of 
the  town  was  supplied  with  water  from  a  mountain  spring,  and  part  from  pri- 
vate wells  from  six  to  twenty  feet  deep.  It  was  noticed  that  all  those  who  used 
the  spring  water  escaped  the  disease,  while  those  who  depended  upon  the  shal- 
low wells  were  stricken  down.  In  all  there  were  many  hundred  cases  and 
about  forty  deaths.  I  secured  some  of  the  water  from  these  shallow  wells  and 
with  it  experimented  upon  a  number  of  cats,  finally  obtaining  the  result  which 
I  announced  to  the  Board  of  Health." 

If,  as  Professor  Vaug"hn  states,  these  city  wells  contain 
fever  germs  enoug"h  to  kill  a  cat,  with  its  traditional  nine 
lives,  what  chance  is  there  for  an  ordinary  human  being-  with 
only  one? 

The  following-  are  the  results  of  a  very  general  examina- 
tion of  the  water  in  wells  in  one  of  the  most  beautiful  and 
well  kept  smaller  cities  in  the  state  of  New  York.  The 
natural  drainage  facilities  of  the  city  are  excellent.  There 
are  no  sewers  worthy  the  name,  however. 

The  results  are  particularly  interesting,  not  only  as 
showing  the  marked  subsurface  pollution  within  a  compara- 
tively few  years,  but  also  as  showing  the  increased  mortality 
directlv  resulting  therefrom. 


24 


THE    SEPARATE    SYSTEM    OF    SEWERAGE. 


"I  have  made  some  chemical  tests  of  water  from  nearly  one  hundred 
wells  to  determine,  if  possible,  the  extent  of  the  pollution  of  the  drinking  water 
commonly  used,  and  have  made  out  a  table  which  is  given  below,  of  the  results 
of  these  tests.  The  amount  of  chlorine  which  a  sample  of  water  may  contain 
and  not  be  regarded  as  unsatisfactory  is  usually  assumed  as  3.5  grains  per  Impe- 
rial gallon.  I  have  drawn  a  line  at  this  point  across  the  list  of  wells  below, 
and  another  at  7.0  grains  per  gallon,  which  last  may,  at  least,  be  called  the 
danger  line  if  not  the  death  line. 

In  the  table  with  the  analysis  of  the  well  water  I  have  placed  those  of 
some  other  waters  for  comparison.  No.  77  was  urine  diluted  with  49  parts  of 
pure  water,  Nos.  85  and  88  are  from  wells  so  situated  as  to  drain  large  barn- 
yards. No.  93  is  from  the  outlet  of  the  sewer  which  last  summer  was  turned 
across  Main  St.  and  carried  down  Mill  St.,  joining  the  Bacon  Street  sewer.  I 
have  also  marked  those  wells  used  by  families  where  there  have  been  cases  of 
fever  and  (generally  fatal)  cases  of  diphtheria  with  an  "  F"  and  a  "  D  "  respect- 
ively. 


.Academy  Filter 

.Thayer  Spring 

.Rain 

.  Hazelton  Spring 

.  Country  Well 

.West  Main 

.Country  Well 

.Lincoln  Avenue 

,  East  Main 

.Wolcott 

.West   Main 

.Wolcott 

.Lincoln 

.South  (i  mile  out) 

.East  Main - 

.Well  in  Pasture , 

•  East  Main 

.Sewer,  Lincoln 

.Spring  in  Pasture 


25 
50 

55 
70 
80 
80 
95 
05 
40 

50 
60 

65 
75 
75 
00 

05 
15 
15 

35 


E                           S                            °  -* 
5                          °                            - 

Z  c/3  U 

20.... West   Main   2.40 

21. ...Summit 2.50 

22....  Myrtle 2.50 

23.... St.    Marks 2.65 

24  ...Church 2.65 

25  . . .  Wolcott 2  70 

26.... Main 270 

27. . .  .Wolcott 2.95 

28 ... .  East  Main 3  00 

29.  .  .  .West  Main 3.20 

30. . .  .Wolcott 3.30 

31 Maple ,.  3.40 

32.... Myrtle 3.50 

33.... Pond  in  Village 3.65 

34.... Myrtle    3.65 

Average    of   9    Rochester  )  „ 

Sewers  (Dr.  Lattimore)  f  •'■' 

35...    Myrtle 3.80 

36 ... . East  Main 4.00 


CHAP.  I. 


IXTRODUCTIOX. 


25 


z  <?.  0 

37 ... .  South 4 

38 ... .  East  Main 4 

39 ... .  East  Main 4 

40.... West   Main 4 

41 ... .  Church 4 

42 ... .  ^lyrtle 4 

43. . .  .Myrtle 4 

44 F 4 

45....  Lake 4 

46 ...  .  Main 4 

47 ... .  South 4 

48 D 4 

49. . .  .Pond  in  Village 5 

50 ... .  Church 5 

51. ...Main 5 

52. . .  .South 5 

53 Lake 5 

54 Lake 5 

55.... West   Main..» 5 

56 North 6 

57    . .  .Clay 6 

58 Church 6 

59 ... .  Craigie 6 

60 Clay 6 

61 Wolcott 6 

62 ... .  Sewer,   East  Mam 6 

63 D.  F 6 

64 ... .  Mill 7. 30 

65 F....  735 

66 ..D....  7,50 

67 ....  St.  Marks 7  60 


25 
25 
35 
50 
50 
60 
60 
65 
65 
75 
00 
00 
20 
25 
65 
75 
75 

GO 
25 
25 
40 

50 
50 

55 
60 


68. 
69. 
70. 

71- 
72. 

73. 
74- 
75- 
76 

77- 
78. 
79 
80. 

Si. 
82. 

83. 
84. 
85. 
86. 

87. 
88. 

89. 
90. 

91- 
92. 

93- 
94. 

95- 
96. 

97 


Bank 7 


.  .Bacon 4 

.  .East  Main 8 

F....  8 

.  .North   9 

D.-.  9 

.  .South 9 

.  .Urine  in  49  pts.  water  .  g 

.  .Lake.  . .    . .  g 

.    Lake 10 

, .  .  East  Main 10 

D.  ..  10 

.  .St.  Mark 10 

D....  II 

,  .  .Myrtle 11 

...Barn  Yard  Well 11 

. . .  Dish  Water 11 

. .  .Myrtle 12 

. .  .Barn  Yard  Well 12 

D 12 

F...  13 

F....  15 

D....  15 

. .  .Sewer,  Mill  St 17 

. .  .West  Main 17 

. .  .Bacon 19 

...Mill 19 

. .  .East  Main 25 

Average  78  wells 6 


60 

70 

25 
80 

85 
85 
00 
10 
60 
65 
75 
50 
70 

75 
90 

05 
30 
75 
90 
20 

75 
80 

65 
00 
60 

30 
70 

05 
80 
50 
56 


26  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

The  following"  table  shows  the  results  of  the  analysis  of 
the  water  supplied  to  Schenectady,  Troy  and  Albany.  The 
Nitrites  were  reduced  to  nitrates  and  both  appear  under  that 
heading-.  Ammonium  salts  are  represented  by  org-anic 
nitrog-en.  The  analysis  was  carried  on  under  the  super- 
vision of  Prof.  Perkins.  The  numbers  represent  parts  per 
100,000  by  weig-ht. 


4 

a 

o 

■s>(jBUJa^ 

J3 
O 

o 

3 

s 

o 

> 

h 

E 
c 

1- 

u. 

(I. 

Uh 

~ 

o 

o       o 

C 

C 

G 

G 

o 

G 

G          C 

00 

in      lO 

m       m       o 

■^         00 

N 

G        m 

anuoiqo 

_ 

P) 

on 

00 

ft 

00                 M 

•^ 

'"' 

N 

M 

0\ 

O          CO 

VO 

m       G 

o 

l-l                PT) 

M 

■<*-      N 

f^ 

c 

o 

t^ 

m       o 

vn 

t^      o\ 

in       n        a 

<- 

-^ 

o 

\a       m 

in 

0           w 

t^       '1- 

m        M 

■S9?EJ}TN 

o 

Tj-       in 
o       o 

O          c!          n! 

m         G 

00 

vO        m 

00 

(I 

-r 

m 

m 

o       o 

Z      Z 

o 

o       o 

GOO 

o       o 

o 

naBojjjN 

o 

o       o 
T       in 

O          O          O 
in       in       in 

G          G 
in        MD 

4) 

oiobSjo 

O 
O 

o       o 
o       o 

GOO 
GOO 

C 

o 

G 

O 

1    ° 

m 

t-^ 

Binommv  aaJ j; 

<U 

(U          <u 

1 

<D        m 

Tr                   1^ 

00 

D          lU 

a 

a       a 

c 

c 

C 

C 

a       a 

o 

o       o 

r 

o       o 

C 

O 

G 

o       o 

z 

^      Z 

^ 

7- 

•z 

Z 

Z      Z 

CT> 

00         o 

o       o 

c 

t^ 

l^^ox 

*"* 

c^      o 

in 

N 

ssaupjBH 

in 

m 

jngnBuijaj 

t^ 

m 

u 

ssaapjBH 

-r 

m 

•jiaBJodui9x 

Tf 

'S- 

o 

;■ 

V-( 

v^ 

1- 

u 

i-< 

v^ 

u 

w 

u 

« 

cd       a 

a 

c 

ns 

n 

ni 

ct 

r 

CS 

•J0103 

1> 

(U         u 

i 

0, 

<U 

a 

0) 

<u 

q 

OJ 

U 

U       U 

L- 

L- 

U 

U 

U 

U 

c 

U 

, 

r- 

G 

in 

f 

M 

^ 

t^ 

c 

^ 

PI         ro 

r- 

tM 

»-( 

•aiBQ 

, 

J3 

, 

^^ 

fO 

a, 
< 

u          u 

<        < 

> 

1- 

c 
< 

L,       rt 

> 

T3 

T 

re 

^' 

> 

C 
J3 

O 

a 

0) 

a 

c 

o 

C 

o 

^ 

CO 

C/) 

7! 

o 

v 

•a[duiBs 

f5 

f^ 

C/} 

<u 

CO 

TJ 

^ 

C/5 

in 

CO 

r 

"o 

CS 

■^ 

^ 

(U 

(D 

V 

CO 

m 

o 

oi 

<u 

^ 

>. 

> 

dJ 

(U 

0) 

Si 

J" 

> 

^      Oi 

c 

a 

c 

s- 

>. 

> 

CO 

a 

<u 

> 

^        cfl 

<T 

rt 

rt 

rt 

3 
J3 

(t 

^ 

ss 

u 

Xi 

J3 

ei 

ni 

rt 

>> 

XI 

in 

H 

< 

<J 

J 

J 

J 

o 

< 

CU 

M 

N 

m 

■<t 

ir 

o 

r~- 

00 

o\ 

o 

M 

ON 

M 

*~* 

28  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

Let  US  now  look  at  these  results  and  see  what  they  indi- 
cate. The  total  hardness  of  the  water  supplied  to  the  three 
cities  is  about  the  same,  the  difference  being"  no  more  than 
would  exist  in  the  same  water  on  different  days.  In  perma- 
nent hardness  the  Troy  water  is  much  better  than  that  of 
Schenectady.  The  nitrates  indicate  the  sewag"e  contamina- 
tion perfectly,  increasing-  as  we  g^o  down  stream  from  Sche- 
nectady to  Albany.  Above  Schenectady  there  is  very  little 
sewag-e  flowing-  into  the  Mohawk,  till  we  reach  Utica,  eig-hty 
miles  above,  that  being-  the  only  place  on  the  river  with  a 
system  of  sewers.  The  river  itself  passes  over  many  rifts 
and  shallows  between  the  places,  affording-  every  opportu- 
nity for  oxydation  of  the  org-anic  matter.  At  Troy  the  river 
has  received  the  sewag-e  of  Cohoes,  Waterford,  Lansing-- 
burg-h,  etc.,  and  at  Albany  that  of  Troy  and  West  Troy  in 
addition,  and  nitrates  according-ly  increase.  The  Hudson 
river  water  at  Albany  has  been  condemned  by  the  Albany 
Water  Commissioner  as  unfit  for  use,  and  a  new  source  of 
supply  has  been  recommended. 

Samples  .5  and  6  were  from  the  same  well — No.  .5  taken 
just  before  it  was  cleaned,  No.  6  about  six  weeks  after. 
There  is  a  vault  a  short  distance  from  the  well,  with  which 
it  is  evidently  in  direct  communication,  the  chlorine  being- 
more  in  the  second  analysis  than  in  the  first.  No.  7  was  fur- 
nished by  a  physician  of  Schenectady  who  was  called  to  pre- 
scribe for  a  man  sick  with  typhoid  fever.  He  suspected  that 
the  cause  lay  in  the  water,  thoug-h  the  man  affirmed  that  it 
was  the  best  water  in  the  city.  The  anah'sis  shows,  besides 
ammonia,  org-anic  nitrog-en,  and  nitrates  in  larg-e  quantities, 
an  amount  of  chlorine  nearly  three  times  as  g-reat  as  that  in 
common  sewag-e. 

In  No.  8  the  nitrates  and  chlorine  were  very  high,  espe- 
cially the  former.  The  well  is  onl}^  eig-hteen  feet  from  a 
vault.  • 


CHAP.  I. 


INTRODUCTION. 


20 


No.  10  was  sent  by  a  physician  of  Albany.  He  writes  as 
follows  concerning"  it: 

"I  send  you  a  specimen  of  well  water,  which  I  think  has  caused  three  cases 
of  severe  illness,  two  of  which  were  fatal.  I  was  called  some  months  after  these 
cases  to  see  a  patient  who  had  a  high  fever,  (temp.  io5'^5,  pulse  140,)  with 
diarrhcea  and  nausea,  in  whom  I  could  find  no  disease  of  any  organ  to  account 
for  the  fever.  I  stopped  the  use  of  the  well  water  and  she  commenced  to 
improve,  and  is  now  (two  weeks)  about  well.  Since  I  saw  her  she  has  been 
drinking  filtered  rain  water.  The  well  in  this  case  is  within  ten  feet  of  a  privy 
vault,  and  the  two  have  adjoined  one  another  for  twenty  years." 

Effect  of  Se^ve^age. — The  beneficial  effects  of  sewerag^e 
are  plainly  seen  in  the  statistics  of  towns  where  an  efficient 
system  has  been  carried  out.  By  sewering"  certain  towns  in 
Eng-land,  the  death  rate  from  pulmonary  diseases  alone  was 
reduced  50  per  cent.  A  marked  decrease  in  the  amount  of 
sickness  and  a  prolong-ation  of  life  has  always  followed 
proper  sanitary  w^orks. 

Below  is  a  table  showing"  the  results  of  sewerag"e  in  six 
towns  in  Great  Britain: 


o«- 

. 

0  0 

0  J3 

q 

.0 

^ 

<u 

"^^ 

(U   0 

0)  0 

& 

S 

•a 

O-D 

>,i: 

a 

0 

°  u. 

NAME  OF  PLACE. 

r8| 

a 

0  «  5 

0  c 

=  8 

(0  «  M 

0)         (fi 

0 

0  V 

.S'-S 

«£•? 

ac  v^ 

5f 

U  0) 

0  >^ 

3  S 

=  s 

t^t 

f%% 

a 

•0  « 

< 

< 

m 

OS 

« 

Cardiff 

33-2 

237 
29.8 

33  2 

22  6 

32 
22 

40 
64 
48 
60 

17 
17 
31 
11 

Croydod  

18  6 

Alacclesfield 

23.7 
26.2 

20 

Merthyr 

18 

Newport 

31.8 
27.5 

21.6 

32 
20 

36 

75 

32 
49 

Salisbury 

21.9 

30  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

"At  Dantzic,  the  deaths  from  enteric  fever  per  100,000 
living-  were  as  follows: 

From  1865  to  1869,  before   any   sanitary   measures   were 
taken,  108. 

From  1871  to  1875,  after  the  introduction  of  water  supply, 
90. 

From  1876  to  1880,  after  the  introduction  of  sewerage,  18." 
The  death  rate  in  London  in  the  last  half  of  the  17th  cen- 
tury was  eig"hty  in  ever}-  thousand.     Now  it  is  about  twenty- 
four  in  every  thousand,  althoug-h  much  more  densely  popu- 
lated. 

Irwin  F.  Smith,  in  a  very  comprehensive  paper  on  the 
^'Influence  of  sewerag^e  and  water  supply  on  the  death  rate 
in  cities"  writes  as  follows: 

"Data  drawn  from  sewered  cities  is  now  available  for  study  and  compari- 
son. To  be  of  service  such  data  must  have  been  carefully  gathered  and  must 
cover  a  considerable  period,  the  population  must  be  known  to  have  been  cor- 
rectly enumerated,  and  various  other  factors  which  enter  into  every  considera- 
tion of  the  death  rate  of  a  place,  such  as  race,  age,  condition  in  life,  crowding, 
occupation,  etc.,  must  be  given  due  weight.  Taking  all  these  factors  into  con- 
sideration, and  casting  up  accounts,  there  remains  a  striking  balance  sheet  in 
favor  of  the  sewered  cities 

In  the  consideration  of  this  subject  the  general  propositions  which  I  wish 
to  lay  down,  and  which  appear  to  me  to  be  clearly  deducible  from  the  data  at 
my  disposal  are  as  follows: 

"Typhoid  fever  and  cholera  decrease  in  proportion  as  a  city  is  well  sew- 
ered. This  may  be  laid  down  as  a  fundamental  proposition  to  which  there  are 
no  exceptions. 

"The  general  death  rate  falls  after  the  sewering  of  a  city,  and,  other  things 
being  equal,   never  again  reaches  the  maximum  of  its  ante-sewered  condition. 

"The  cost  of  building  and  maintaining  sanitary  works  is  inconsiderable  in 
comparison  with  the  direct  pecuniary  loss  by  sickness  and  death,  which  their 
absence  entails. 

"Drains  imperfectly  jointed  and  lacking  the  proper  facilities  for  flushing 
or  the  necessary  fall  for  the  introduction  of  excreta  and  for  proper  clearing,  are 
in  no  proper  sense  of  the  word  sewers,  and  are  not  considered  as  such  in  this 
paper.  If  excreta  be  introduced  into  such  drains  it  almost  always  proves  a 
public  nuisance,   and  the  writer  is  far  from  denying  that  under  some  circum- 


CHAP.   I.  INTRODUCTION,  31 

stances  such  drains,  "sewers,"  so-called,  may  not  become  active  promoters  of 
infectious  diseases.  When  I  speak  of  the  benefits  arising  from  sewerage,  I 
mean  invariably,  modern  sewers,  well  built,  well  ventilated — the  soil-pipes, 
traps,  water-closets,  etc.,  being  constructed  on  approved  plans  and  in  the  most 
workmanlike  manner. 

My  reason  for  selecting  typhoid  fever  is  that,  although  the  nature  of  the 
typhoid  poison  is  yet  in  dispute,  we  now  understand  very  clearly  the  manner  in 
which  the  disease  is  spread.  Another  reason  is  the  gravity  of  the  mortuary  tax 
levied  by  typhoid  fever.  This  will  be  at  once  apparent  if  we  consider  briefly 
the  statistics  of  this  disease." 

The  following-  graphical  presentations  of  some  of  the  sta- 
tistics collected  b}'  Mr.  Smith  are  reproduced  from  his  paper. 


DEATHS  FROM  TYPHOID  FEVER  TO  EACH  10,000  INHABITANTS 

BEFORE,  DURING  AND  SINCE  THE 
INTRODUCTION  OF  SEWERAGE  AND  WATER  SUPPLY. 


No.  of  Deaths 
Per  10,000 

1861-59 

.5^ 

B 

ES 

1860-65 
1866-73 

1874-84 

•i    1863-72 

"i    1873-85 

1863-75 

1876-80 

aa 

1881-84 

1851-66 
1867-76 

1877-84 

CQ 

1854-73 
1873-77 

1878-84 

o3 

a 

6^ 

1866-73 
1874-79 
1880-84 

"3 

1865-69 
1870-74 

CO 

1875-84 

1838-58 

1 

1859-65 
1866-84 

1850-70 
^  1870-80 

"  1881-84 

03 

fee 

1850-71 

1872-75 

Ed 

1876-83 

s 

1847-59 
1860-69 

!B= 

1870-84 

1846-49 

J 

1850-59 

1860-69 

1870-81 

CO 

1848-62 
1867-79 
1880-84 

-cvim.hio©t-Qoo)2  =  2i22221:2®8N 


13.3 


2.4 


9.3 


7.4 


1.5 


9.2 


7.6 


2.9 


13.0 


3.1 


10.0 


10.3 


I    9.3 

9.0 

9.0 


6.6 


17.4 




(/I 

00 

rt 

to 

^ 

m 

_>, 

t* 

, 

•"5. 

^ 

C/5 

Cu 

UJ 

3 

1      ■< 

;_, 

H 

OJ 

1        1 

^ 

rt 

u 

>> 

a 

'53 

z 

a 

<c 

3 

H 

_ 

m 

CO 

TJ 

1    ;': 

Qu 

L. 

Si  t- 

o; 

O 

■4-> 

m 
Eh 

Q^ 

OJ 

w      >, 

Z 

■ZD 

< 

UJ 

"O 

^T, 

S 

CO                                                               en 

Q 

o    a 

a: 

i~                                         g 

Z 

. 

O 

2i  fe 

< 

CD 

bo 

-  1 

o 

^ 

rt 

^ 

0 

z 

CD 

(D 

^   £ 

- 

q 

< 

y 

CO 

CO 

2|    . 
1  i-t 

o 

a; 

2 

Qi 

O 

«4- 

C   '"     c 

« 

E 

a. 
a: 

C-l 

<! 

< 

z 

Q 
0^ 

o 
® 

O 

c  . 

CD 
3 
«»- 

water,  and  in 
rely  destitute  ( 
uality  and  qui 

X 

< 

U 

£ 

T3    -5     C^ 

2    c    c 

Q 

•  - 

—         -i- 

ck: 

ijj 

O 

^1'^ 

'■£■ 

UJ 

1 

> 

■B   S| 

—J 
O 

h 

O 

q: 

D 

Q 

4J 

o 

-a    2i    c 

n 

X 

0 

U      (U      1> 

U 

u 

f- 

Q. 

O 

r. 

-M 

ndantly  supp 
ompletely  se 
illy  very  defi 

< 

^ 

ll°l 

■       1 

o 

=     i^     ^- 

II        1 

< 

CO 

a  '      a 
^s     '^     "^ 
S    S3    ^ 

ll-l. 

O 

0 

■(-> 

■a 

t    ^    c 

■  h^  'S 

KH       H^       J3 

:::::":•::•  ui 
;    :    :  ^    :    :    :    ;    :  O    :    ;  J 

® 

c 

Q 

0.      0.        - 
D     D     C 

■      w 

:    :     :  H    :    :    :    :    :  D    :    :  O 

lies  of  Gro 
ties  of  Gro 
to  infectic 

LOCALl 

W  YORK  . . 

OOKLYN  .. 
STON     

z 
z 

'■     < 
:     a 

<      > 

T.  LOUIS.... 

HICAGO 

INCINNATI. 
EMPHIS  (Te 
ARSEILLES, 

OULON 

APLES 

ALERMO 

AURIU 

T.  PETERSU 
RUSSELS... 
RESLAU  .... 
ONSTANTIN 

< 
Q 

'^    ■—      c 

1  W  B!  O  O  iJ       W 

O         U         Q^ 

j3    XI     o 

1  z  oa  oa  J  o  II  z 

c/iuoSShZcuS^axu 

< 

ggggg       g 

CO  «o  tc  ?D   »;5  *.■?  tc  CO   o  «o  ift   :r   i.'S 

cD?o?o:o?ospw:ocoa3:o:;iC 

o 

X3     30     CO     X'     OO            X) 

xxooooxxXaoacxxgx 

'"^    ^^            f— 1 

a 

1 

II 

34  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

Schenectady,  N.  Y.,  was  sewered  in  1884.  The  Health 
Of&cer,  H.  C.  Van  Zant,  in  his  report  for  1887  writes  as  fol- 
lows: 

"I  remark  this  fact:  in  1883,  twenty-six  deaths  occurred  from  typhoid 
fever;  1885,  eighteen  deaths  occurred  from  the  same  cause;  1887,  five  deaths 
are  recorded  as  produced  by  typhoid  fever.  More  deaths  in  1883  than  cases  in 
1887.     The  inference  is  easy." 

The  desirability  of  the  removal  of  filth  from  cities  is  no 
longer  a  matter  of  doubt.  The  beneficial  effects  of  a  proper 
system  of  sewerage  is  proven  by  abundant  statistics.  The 
results  are  shown  in  a  decrease  of  disease,  a  lowering  of  the 
death  rate,  and  in  turning  plague  smitten  cities  into  health- 
ful ones.  The  question  no  longer  is,  shall  it  be  done?  but, 
how  shall  it  be  done? 

Systems  in  Use. — The  different  systems  for  the  removal 
of  excrement  and  liquid  refuse  may  be  divided  into  three 
classes,  viz.:  by  "Direct  Removal,"  by  the  "Pneumatic  Sys- 
tem," and  by  "Water  Carriage."  Under  the  head  of  "Direct 
Removal,"  the  principal  methods  are  the  "Pail  System"  and 
the  "Dry  Earth  Closet." 

In  the  Pail  System  the  excreta  is  caught  in  a  pail  or  tub 
and  removed  in  carts  at  intervals,  varying  from  one  day  to  a 
week.  This  system  is  used  in  many  large  cities  in  Europe, 
and  is  advocated  by  eminent  authorities.  But  the  exchange 
and  cleansing  of  the  pails  need  to  be  enforced  by  such  strict 
police  regulations  as  would  be  difficult  to  carry  out  in  the 
United  States.  There  are  several  modifications  of  the  Pail 
System.  In  one,  the  fluids'  are  allowed  to  filter  through  a 
sieve  and  run  off  into  the  sewers  provided  for  the  storm 
water,  so  that  only  the  solid  matter  is  carried  away  in  the 
carts.  In  another,  the  tub  is  lined  with  some  material,  which 
acts  as  an  absorbent  and  deodorizer,  as  in  the  Goux  system. 

When  the  Dry  Earth  Closet  is  used,  dry,  powdered 
earth,  or  ashes,  is  added  to  the  excreta  in  sufficient  quanti- 
ties to  absorb  the  moisture  and  deodorize  the  whole  mass. 
So  much  care  and  attention  is  necessary  to  provide  a  proper 


CHAP.  I.  INTKODUCTION.  35 

supply  of  dry  earth,  to  apply  it  properly,  and  to  attend  to  its 
removal,  that  it  can  only  be  used  in  exceptional  cases,  and 
cannot  be  relied  upon  for  g^eneral  use. 

To  obviate  the  difficulty  of  the  frequent  exchang-es  and 
constant  supervision  necessary  to  the  successful  operation 
of  the  Pail  System,  water-tig-ht  cess-pools  are  sometimes 
used.  They  are  made  larg-e  enoug-h  to  hold  the  sewag^e  for  a 
considerable  time  and  when  filled,  the  sewag"e  is  carried 
away.  The  nuisance  of  emptying-  them  is  somewhat  abated 
by  the  use  of  a  larg-e  air-tig-ht  iron  tank,  mounted  on  wheels. 
The  air  is  exhausted  from  the  tank,  and  by  making-  a  pipe 
connection  between  the  interior  of  the  tank  and  the  sewag-e 
in  the  cess-pool,  the  contents  of  the  cess-pool  are  forced  by 
atmospheric  pressure  into  the  tank;  or,  the  sewag-e  may  be 
pumped  from  the  cess-pool  into  the  tank. 

The  three  principal  "Pneumatic  Systems"  are:  the 
"Liernur, "  "Berlier, "  and  "Shone." 

The  Liernur  and  Berlier  systems  consist  essentially  of  a 
network  of  air-tig-ht  iron  pipes,  throug-h  which  the  excremen- 
titious  matter  is  drawn,  by  exhausting-  the  air  from  the  pipes 
by  means  of  larg-e  air  pumps. 

These  systems  are  intended  to  dispose  of  only  that  part 
of  the  household  wastes  which  is  most  valuable  for  manure. 
Separate  conduits  must  be  provided  for  the  foul  liquid 
wastes  from  dwelling-s,  factories,  etc.  The  necessary  plant 
and  appurtenances  are  very  expensive,  and  even  then  these 
systems  only  partly  answer  the  purpose  of  sewers. 

The  prominent  feature  of  the  Shone  S3'st€m  is  the  use 
of  compressed  air  for  the  purpose  of  raising-  sewag-e  from  a 
low  level  to  a  hig-her  one.  It  is  especially  valuable  in  towns 
where  sufficient  fall  for  sewers  cannot  be  obtained.  In  this 
plan,  the  sewage  is  conducted  throug-h  pipes  in  the  ordinary 
wa}"  until  it  becomes  necessary  to  carry  it  to  a  higher  level. 
It  then  flows  into  a  larg-e  iron  tank,  called  a  "Pneumatic  • 
Ejector."     (See  cut.)     When  the  Ejector  is  full,  compressed 


36 


THE    SEPARATE   SYSTEM    OF    SEWERAGE. 


air  is  automatically  applied  to  force  the  sevvag-e  into  pipes  at 
a  hig'her  level,  when  it  is  ag"ain  allowed  to  flow  onward 
towards  the  outfall  under  the  influence  of  g-ravity,  or 
directly  through  a  discharge  pipe  to  the  point  of  outfall. 
Shone  Ejectors  ma}'  also  be  utilized  to  deliver  the  sewag^e 
from  an  outlet  below  low  water  level.  The  air  is  com- 
pressed by  steam  or  water  power,  at  a  central  station  and  is 
led  by  pipes  to  the  Ejectors,  so  that  they  can  be  placed  in 
any  convenient  situation,  and  as  frequently  as  the  case  may 
require. 


CHAP.  I.  INTWODUCTIOX.  37 

In  many  instances  the  air  compressing'  machinery  is 
located  at  a  water  pumping-  station,  and  thus  the  wag-es  of 
special  attendants  necessary  to  operate  an  ordinary  sewag"e 
pumping"  station  obviated. 

The  Shone  Ejector  takes  the  place  of  a  pump  for  raising- 
sewag-e,  and  can  be  used  with  great  advantag^e  in  situations 
where  it  would  be  difficult  to  bring-  the  sewag-e  to  one  pump- 
ing- station. 

The  Shone  S3'stem  is  extensively  used  in  Eng-land.  In 
this  country  it  is  in  operation  in  Chicago,  Winona,  Minn,, 
Worcester,  Mass.,  Lynn,  Mass.,  Fair  Haven,  Mass.,  Ithaca, 
N.  Y.,  White  Plains,  N.  Y.,  Charleston,  S.  C,  Portsmouth, 
Va.,  Far  Roc ka way,  L.  I.,  etc. 

All  of  the  systems  of  direct  removal  require  constant 
care  and  attention,  and  only  partially  accomplish  the  end  in 
view.  They  are  better  than  no  system,  but  are  not  as  effi- 
cient or  as  easily  managed  as  the  method  of  "water  car- 
riage" or  sewerage.  Water  is  the  great  scavenger.  It 
cleanses  our  houses,  our  clothes,  our  food,  and  ourselves; 
and  having  once  been  soiled  it  must  be  gotten  rid  of.  In 
doing  this,  the  water  may  be  made  the  vehicle  for  carrying 
away  excrementitious  matter,  which  would,  by  putrefaction, 
vitiate  the  air  and  tend  to  produce  disease. 

In  the  Pneumatic  Systems  costly  machinery  is  neces- 
sary to  provide  for  carrying  away  only  a  portion  of  the 
refuse  which  should  be  disposed  of,  and  the  expense  of  ope- 
rating is  large  and  constant. 

The    Water   Carriage   System   is   most   favored   by   the 

leading  English,  German,  French  and  American  sanitarians. 

"As  ordinarily  managed,  the  earth  closet  and  all  other  conservancy  methods 

become    a   nuisance,    only    to    be  tolerated  when  sewerage  proper  cannot   be 

secured." — h-win  F.  Smith. 

"I  do  not  say  that  a  well  managed  conservancy  system  is  not  better  than  a 
badly  managed  one,  nor  far  better  than  no  system  at  all,  nor  do  I  say  that  there 
are  not  places  where  the  difficulty  of  carrying  out  a  Water  Carriage  System  is 
not  so  great  as  to  be  almost,  if  not  quite,  insurmountable;  but  I  do  say  that  in 
towns  where  a  Water  Carriage  system  is  possible,  there  is  no  room  for  choice  in 
the  matter." — Corjield 


38  THE   SEPARATE   SYSTEM    OF    SEWERAGE. 

In  the  Water  Carriag^e  System,  all  that  is  needed  is  a 
comparatively  inexpensive  conduit  which  provides  for  all  of 
the  sewag-e;  and  if  properly  constructed  the  cost  of  mainte- 
nance is  trifling-. 

There  are  many  cities  which  have  provided  themselves 
with  an  abundant  supply  of  water,  and  yet  have  made  no 
provisions  for  a  system  of  sewers.  Increasing-  the  water 
supply  without  providing-  for  its  outflow  after  it  has  been 
fouled,  only  makes  a  bad  matter  worse.  The  number  and 
size  of  the  cess-pools  must  be  increased.  Instead  of  drain- 
ing- the  soil,  as  common  sense  would  dictate,  additional  water 
is  poured  into  it  by  the  millions  of  g-allons,  and  year  by  year 
the  soil  is  more  thoroug-hly  soaked  with  sewage.  The 
streams  of  filthy  water  which  may  be  seen  running-  in  the 
open  drains,  leading-  from  back  yards  into  the  streets,  tell  a 
story  which  all  can  read,  and  the  effects  of  this  state  of 
affairs  can  be  plainly  seen  if  the  Health  Officer  makes  full 
reports. 

One  of  the  twelve  tasks  imposed  upon  Hercules  was  to 
cleanse  the  stables  of  Aug-eas.  In  these  stables  vast  herds 
of  cattle  had  been  kept  for  many  years,  and  they  had  never 
been  cleaned.  He  accomplished  the  task  by  turning-  a 
stream  of  water  throug-h  them.  This  famous  exploit — 
"cleansing-  the  Aug-ean  stables" — is  repeated  over  and  over 
again  wherever  abundant  water  supply  is  supplemented  b}^ 
thoroug-h  sewerag-e.  Had  Hercules  only  planned  to  bring- 
the  water  into  the  stables  and  made  no  provision  for  its  out- 
flow, the  project  would  have  been  a  miserable  failure,  and 
the  sensible  people  of  that  day  would  have  called  Hercules  a 
fool;  and  yet  there  are  cities  even  in  this  enlig-htened  ag-e, 
where  such  a  plan  has  been  pursued. 

"The  yearly  discharge  from  the  sewers  of  Brooklyn  equals  in  volume  what 
would  fill  the  entire  streets  and  avenues  of  the  city  to  a  depth  of  twelve  feet 
above  the  pavement  or  three  feet  over  every  parlor  floor  in  the  city.  Such  is 
the  amount  of  work  silently  going  on  beneath  our  feet,  of  which  we  take  no 
note  save  when  it  is  interrupted  "—Adams. 


CHAPTER  II. 

WATER  CARRIAGE  SYSTEMS. 

A  theoretically  perfect  sewer  would  be  one  in  which  all 
of  the  sewag"e  would  be  carried  rapidly  to  its  outfall  outside 
of  the  city,  so  that  no  time  would  be  g^iven  for  decomposition. 
The  conduit  itself  should  be  smooth,  impervious  to  water, 
and  should  be  water  tig"ht  throug^hout  its  entire  length.  It 
should  be  flushed  at  intervals,  and  so  thoroug-hly  that  the 
development  of  any  considerable  amount  of  sewer  gfas  would 
be  impossible. 

It  should  be  so  well  ventilated  that  the  small  amount  of 
sewer  g-as  which  mig-ht  unavoidably  be  g'enerated  in  the 
sewer  would  be  so  diluted  with  fresh  air  as  to  be  rendered 
harmless. 

It  should  be  provided  with  ample  means  for  inspection 
and  repair. 

It  should  be  automatic  in  its  action,  so  as  to  require  the 
least  possible  amount  of  care  and  attention. 

One  of  the  first  questions  which  presents  itself  to  the 
eng-ineer  in  planning-  a  system  of  sewers  is,  whether  the 
sewers  shall  be  made  larg-e  enoug-h  to  carry  the  storm  water 
as  well  as  the  sewag-e,  or  the  sewag-e  only.  When  a  system 
of  sewers  is  desig^ned  to  carry  both  the  storm  water  and  the 
sewag"e,  it  is  called  the  "Combined  System."  When  the  sys- 
tem is  desig-ned  to  carry  only  the  sewag^e  proper,  that  is,  the 
liquid  refuse  from  dwelling's,  factories,  etc.,  it  is  called  the 
"Separate  System." 

The  Combined  System. ^ — The  largfe  sewers  of  the  Com- 
bined System  are  usually  built  of  brick.  The  brick  beings 
porous,  allows  more  or  less  of  the  sewag'e  to  escape  into  the 


40  THE   SEPARATE    SYSTEM    OF   SEWERAGE. 

soil,  even  if  every  joint  is  water-tig^ht,  which  is  never  the 
case.  The  roug-h  surface  of  the  bricks  soon  become  covered 
with  a  slime  of  organic  matter,  which  is  constantly  decom- 
posing". In  desig-ning-  sewers  on  this  system  the  size  will  be 
determined  mainly  by  the  amount  of  rainfall  per  hour  during 
storms,  and  the  surface  to  be  drained.  The  volume  of  rain- 
fall to  be  provided  for  is  so  much  more  than  the  sewage,  that 
the  amount  of  sewage  scarcely  enters  into  the  computation.* 

It  is  readily  seen  that  ordinarily  the  sewage  will  be  but  a 
trickling-  stream  in  a  sewer  large  enough  to  carry  the  storm 
water.  At  the  street  corners  are  catch-basins  into  which 
the  storm  water  passes  on  its  wa}"  to  the  sew^er.  Here  the 
sand  and  rubbish,  carried  along  by  the  current  from  the 
street,  is  supposed  to  settle  and  remain  in  the  basin,  while 
the  water  passes  through  a  trap  into  the  sewer.  In  the  rush 
of  water  during  a  storm,  however,  a  considerable  quantity  of 
the  material  which  is  supposed  to  remain  in  the  catch-basin 
is  carried  on  into  the  sewer,  and  this,  with  other  foreig-n 
substances,  introduced  into  the  sewer  either  by  accident  or 
malice,  settles  on  the  bottom.  These  obstructions  form  a 
series  of  small  dams  in  the  sewer,  and  in  dry  weather  the 
sewage  stands  in  a  succession  of  pools  along-  the  sewers, 
decomposing  and  sending  volumes  of  sewer  gas  out  of  every 
crevice  through  which  it  can  escape. 

The  great  size  of  the  conduits  of  the  Combined  System, 
it  is  seen,  is  detrimental  to  their  efficiency  in  removing-  sew- 
ag-e  rapidly  and  completely;  and  yet,  for  the  purposes  for 
which  they  are  supposed  to  be  designed,  they  are  seldom 
large  enough.  Even  where  vast  sums  have  been  spent  to 
construct  the  Combined  System  of  sewers,  it  is  seldom,  if 
ever,  that  they  will  carry  the  water  of  great  storms.  In 
man}'  cities — notably  Chicago  and  London — where  money 
has  been  poured  out  without  stint,  and  millions  of  dollars 
have  been  expended  for  sewers  of  great  size,  the  extraordi- 

*See  chapter  specially  devoted  to  this  subject. 


CHAP.    II.  WATKK    CAWKIAGP:    SYSTIOMS.  41 

nary  storms  are  not  provided  for,  and  the  consequence  is 
that  the  sewers  overflow,  and  cellars  and  basements  are 
flooded  with  sewag^e.  Where  the  storm  water  is  excluded 
from  the  sewers,  or  only  a  definite  amount  admitted  for  the 
purpose  of  flushing-,  no  such  disaster  can  occur. 

The  difficulties  of  properly  flushing-  and  ventilating 
large  sewers  are  almost  insurmountable.  Manv  devices 
have  been  proposed  for  ventilation.  Some  have  advocated 
hig-h  chimneys  with  a  fire  in  them  to  produce  a  draught.  Oth- 
ers, a  shaft  with  a  screw  or  fan,  for  producing  a  current. 
None  of  these  plans  have  proved  efficient,  and  there  seems  to 
be  no  way  of  disposing  of  the  g-as  except  to  let  it  out  into  the 
street  by  openings  from  the  sewer  to  the  pavement.  In  any 
dry  season,  when  there  is  the  least  amount  of  sewage  and, 
therefore,  the  most  sluggish  flow  and  the  greatest  evolu- 
tion of  gas,  the  water  evaporates  from  the  catch-basin  trap 
and  there  is  nothing  to  hinder  the  escape  of  gas  into  the 
streets.  The  catch-basin  itself,  unless  kept  clean,  soon 
becomes  a  cess-pool,  charged  with  filth  from  the  streets  and 
gutters,  which  soon  decomposes. 

The  flushing  cannot  be  very  thoroughly  accomplished, 
owing  to  the  rough  interior  surface  of  brick  sewers,  and  to 
the  large  amount  of  water  necessary  in  the  large  sewers. 
The  most  that  can  usually  be  done  is  to  produce  current 
enough  to  carry  forward  and  out  of  the  sewer  the  solid  mat- 
ter and  rubbish,  which  would  obstruct  the  flow  of  the  sew- 
age. Sometimes  the  sewage  itself  is  stored  up  until  a  suffi- 
cient volume  is  collected  to  flush  the  sewer,  when  it  is 
released. 

These  points  are  so  well  brought  out  in  the  annual 
report  of  O.  W.  Wight,  A.  M.,  M.  D.,  Health  Officer,  Detroit, 
Mich.,  to  the  Common  Council,  that  we  quote  quite  fullv 
from  his  report: 

"Ditches,  gutters,  tiles  and  porous  brick  conduits  for  removing  surface  and 
subsoil  water  are  comparatively  cheap.      It  adds  immensely  to  the  cost  to  trans- 


42  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

form  water  drains  into  sewers,  so  as  to  make  them  at  all  fit  to  convey  liquid 
wastes.  The  combined  expense  of  a  separate  drainage  system  and  an  inde- 
pendent sewer  system,  is  much  less  than  the  expense  of  a  single  system  that 
cannot  be  so  constructed  as  to  perform  well  the  double  service  of  removing 
water  from  the  soil  and  liquid  from  habitations. 

"In  most  places  it  is  not  difficult  to  find  a  proper  out-fall  for  the  water  of 
a  drainage  system.  As  soon  as  sewage  is  mixed  with  the  flow  of  drains  the 
whole  mass  is  contaminated,  and  the  trouble  and  cost  of  securing  a  safe  out-fall 
are,  as  a  rule,  greatly  increased.  The  necessity  of  pumping  vast  quantities  of 
rain  water  and  subsoil  water,  mingled  with  the  liquid  refuse  of  houses  and  fac- 
tories in  the  same  system  in  the  new  sewerage  works  of  Berlin  and  Dantzic, 
increases  the  running  expenses  to  an  extent  threatening  failure. 

"The  sewage  proper  of  a  city  is  nearly  a  constant  quantity.  It  is  approxi- 
mately measured  by  the  amount  of  water  daily  used  in  houses  and  factories. 
Consequently,  the  engineer  in  constructing  a  system  for  the  removal  of  sewage 
proper,  can  adapt  it  to  a  constant  flow  and  make  it  self  cleansing.  On  the  con- 
trary, rain-fall  is  an  immensely  variable  quantity.  A  drainage  system  for  its 
removal  must  be  of  maximum  size.  When  sewage,  therefore,  is  turned  into 
the  drainage  system,  a  slow  flow  will  be  inevitable  much  of  the  time,  resulting 
in  putrefaction  and  the  generation  of  sewage  gas,  the  presence  of  which,  within 
the  area  of  inhabited  places,  dangerously  violates  the  mcst  vital  law  of  sanitation. 

"In  the  drainage  system  all  conduits  are  purposely  made  to  let  water  in. 
The  object  is  to  convey  water  away  from  the  soil  But  a  porous  drain  will 
strain  sewage  through  into  the  earth,  and  gradually  pollute  it.  Consequently, 
a  conduit  for  the  conveyance  of  sewage  must  be  made  tight.  Hence  the  abso- 
lute incompatibility  of  the  two  ends  sought  in  the  same  structure.  A  good 
sewer  is  a  bad  drain.  A  good  drain  is  a  dangerous  sewer.  Attempts  are  con- 
stantly renewed  to  attain  the  double  quality  of  perviousness  from  without  and 
imperviousness  from  within,  with  unceasing  and  inevitable  failure.  Sanita- 
rians who  are  quacks  in  engineering  have  tried  it  in  vain;  engineers  who  are 
quacks  in  sanitation  have  tried  it  equally  in  vain.  Quacks  in  both  engineering 
and  sanitation,  sometimes  well  represented  in  City  Boards  of  Public  Works, 
obstinately  keep  up  their  search  for  the  unattainable,  like  the  seekers  for  the 
philosopher's  stone  and  the  inventors  of  perpetual  motion. 

"Water  stored  in  cisterns  is  almost  invariably  poisoned  by  the  way  of 
overflow  pipes  which  discharge  into  the  sewer  system  of  inhabited  places  and 
return  the  dangerous  gas.  And  the  drain  pipes  from  cellars  and  basements 
generally  furnish  avenues  through  which  this  invisible  foe  of  human  life  in 
cities  finds  easy  ingress  to  habitations.  A  separate  drainage  system  affords  an 
easy  means  of  guarding  against  peril  from  such  a  source  Sanitary  inspectors 
are  often  astounded  by  finding  a  tube  from  an  ice  box,  in  which  choice  and  del- 
icate food,   like  meats  and  milk,   is  kept,   running  directly  into  a  sewer  pipe. 


CHAP.  II.  WATKK    CAKKIAGK    SYSTEMS.  43 

The  combined  sanitary  and  engineering  quack  will  tell  you,  with  pitiful  igno- 
rance, that  the  deadly  sewer  gas  is  kept  out  by  means  of  a  little  water  trap 
through  which  a  baby  could  blow  with  a  straw.  A  separate  system,  used 
exclusively  for  sewage,  is  the  only  certain  safety  against  such  danger. 

"With  the  clumsy,  costly,  perilous  Combined  System  in  general  use  for 
removing  water  and  sewage  together,  the  earth  of  towns  gradually  becomes 
infected  with  organic  matter  in  a  state  of  putrescence.  Hence  the  water  of 
springs  and  wells  at  length  becomes  polluted  and  unfit  for  use.  With  a  sepa- 
rate, properly  constructed  and  properly  managed  system  of  impervious  pipes 
for  the  removal  of  all  sewage,  and  with  other  sound  sanitary  regulations  for  the 
care  and  removal  of  solid  organic  refuse,  there  is  no  reason  why  the  spring 
water  and  well  water  in  towns  should  not  remain  clean  and  wholesome. 
Besides,  when  the  earth  of  inhabited  places  is  kept  so  clean  as  to  preserve  the 
purity  of  the  water,  no  exhalations  will  arise  from  it  deleterious  to  health  and 
dangerous  to  life. 

"This  is  not  the  place  to  describe  in  detail  the  separate  sewer  systems  for 
the  removal  of  liquid  organic  wastes  from  inhabited  places.  The  engineer 
must  conform  to  the  requirements  of  sanitary  science.  Any  system  will  be 
faulty  which  allows  sewage  to  putrefy  at  all,  either  in  its  source,  on  its  journey 
from  human  abodes,  or  in  its  outfall.  *  *  *  *  The  great  principle  to  be 
kept  in  view  is  the  removal  of  sewage  (not  sewage  diluted  with  vast  quantities 
of  surface  and  subsoil  water)  without  pollution  of  the  soil,  without  putrefac- 
tion, and  consequently  without  generation  of  sewer  gas  on  the  journey.  *  *  * 
The  soil  where  man  dwells  is  sacred,  and  it  is  sanitary  sacrilege  to  pollute  it. 
He  who  fouls  the  air  that  he  breathes  himself,  or  the  water  that  he  drinks,  or 
the  food  that  he  eats,  is  a  barbarian  who  might  learn  wisdom  from  the  cat  or 
decency  from  any  swine  not  demoralized  by  contact  with  man.  He  who  fouls 
the  air  that  another  must  breathe,  or  the  food  that  another  must  eat,  or  the 
water  that  another  must  drink  is  a  criminal,  to  be  classed  with  those  who  maim 
and  kill. 

"There  are  more  reasons  for  such  care  in  the  removal  of  organic  wastes 
from  inhabited  places  than  appear  on  the  surface.  The  chemistry  and  hygiene 
of  putrefaction  are  complex,  involving  many  practical  considerations.  Wher- 
ever there  is  a  collection  of  putrefying  organic  matter,  whether  on  the  ground, 
in  the  ground,  within  a  faulty  sewer,  or  under  a  habitation,  there  is  a  tireless 
foe  to  health  and  life.  Not  only  are  putrescent  collections  of  garbage,  decay- 
ing vegetables,  manure,  offal  and  human  excreta  harmful  in  themselves,  by 
reason  of  exhalations  poisoning  the  air  and  leeching  liquids  polluting  the  earth; 
they  are  also  depositories  and  multipliers  of  disease  germs.  Such  collections 
may  not  produce  infectious  diseases  dd  novo,  but  they  lessen  the  vitality  of  peo- 
ple living  in  the  neighborhood,  and  thereby  lessen  the  power  of  resisting  epi- 
demics.    It  is  a  well  known  pathological  fact  that  nature  struggles  to  eliminate 


44  THE    SEPARATE   SYSTEM    OF    SEWERAGE. 

disease  by  excretory  processes.  Accumulations  of  filth  containing  excreta  may, 
therefore,  harbor  seeds  of  various  communicable  maladies.  Sewer  gas,  while 
it  may  not  beget  scarlatina,  diphtheria,  smallpox  and  other  contagious  diseases, 
easily  becomes  the  vehicle  of  conveying  them,  through  obscure  and  intricate 
channels.  *  *  *  a  foul  sewer,  swarming  with  scarlatina  germs,  may  be 
more  dangerous  to  a  neighborhood  than  an  infected  school-house.     *     *     * 

"It  has  been  objected  in  relation  to  separate  systems  for  drainage  and  the 
removal  of  sewage,  that  droppings  of  horses  and  other  animals  in  the  street, 
steeping  in  the  rain-fall,  will  be  a  source  of  pollution  to  surface  water,  render- 
ingQit  putrescible,  and  consequently,  capable  of  generating  sewer  gas.  The 
simple  and  effective  remedy  is  cleaning  the  streets  frequently  and  well.  Most 
cities  would  thereby  be  greatly  improved,  both  in  appearance  and  salubrity. 

"It  has  also  been  objected,  that,  in  quarters  where  the  vitrified  sewer  pipe 
system  for  the  removal  of  sewage  does  not  extend,  there  the  inhabitants  must 
throw  the  liquid  wastes  of  household  life  upon  the  gro.und.  No  such  necessity 
exists.  Even  an  isolated  habitation  in  the  country  should  have  its  sewer  pipes, 
and  entirely  separate  from  the  drainage  system,  to  convey  kitchen  slops,  wash- 
water  and  other  dangerous  liquids  to  a  place  of  safety.  The  reason  why 
typhoid  fever,  diphtheria,  and  some  other  filth  diseases  are  so  prevalent  in 
country  districts,  is  that  privy  vaults  so  frequently  seep  into  wells,  and  animal 
excreta  of  pig  pens  and  stables  are  left  to  poison  the  earth  and  the  air.  •  The 
ground  about  kitchens,  super-saturated  with  slops,  very  often  becomes  putres- 
cent in  the  summer  warmth,  breeding  disease  which  superstitious  ignorance 
attributes  to  Heaven.  A  householder  may  dispense  with  his  parlor  and  its 
adornments,  if  necessary,  but  he  cannot  afford  to  invite  upon  himself  and  fam- 
ily disease  and  death  by  neglecting  to  provide  the  means  of  keeping  the  site  of 
his  habitation  dry  and  clean.  Laborare  est  orare — 'to  labor  is  to  pray'^said 
the  wise  old  monk,  and  the  most  effective  prayer  for  health  is  to  supply  every 
needed  hygienic  device  for  the  sacred  home  of  the  family 

"It  is  further  objected  that  most  of  the  cities  are  sewered  for  the  double 
purpose  of  removing  storm  water  and  sewage  through  the  same  conduits,  and 
that  we  cannot  afford  to  do  the  costly  work  over  again.  It  is  one  of  the  fates  of 
Progress  that  faulty  methods  must  be  followed  by  reconstruction.  No  works 
last  forever,  and  when  we  build  anew  we  can  do  it  better.  In  the  meantime 
the  faulty  sewers,  with  their  dangerous  debauchment  into  the  nearest  stream, 
lakes,  or  ocean  harbor,  can  be  washed  out,  disinfected,  and  used  exclusively  for 
water-drainage  while  a  supplementary  system,  with  safe  out-fall,  for  the  removal 
of  sewage  alone,  is  constructed  with  proper  engineering  skill  under  the  direc- 
tion of  sanitary  science.  The  cost  of  such  a  supplementary  system  is  not  more 
than  one-fourth  of  that  of  the  prevailing  system." 


CHAP.   II.  WATICK    CAKKIAGK    SYSTICMS.  45 

Subsoil  Drainage. — In  some  instances  it  will  be  neces- 
sary to  lay  special  drains  for  the  removal  of  ground  water. 
It  will  be  found,  however,  that  often  the  strata  are  so  broken 
up  by  dig-g-ing"  the  trench  for  the  sewer  and  refilling"  it,  that 
the  level  of  the  g-round  water  will  be  materially  lowered. 
This  is  especially  the  case  when  the  soil  is  made  up  of  alter- 
nating- strata  of  pervious  and  impervious  material  with  an 
inclination  unfavorable  to  the  escape  of  the  gfround  water. 

Nothing-  connected  with  desig-ning-  and  building-  a  sys- 
tem of  sewers  calls  for  more  discretion  on  the  part  of  the 
eng-ineer  than  proper  provision  for  the  g-round  water.  It  has 
frequently  happened  that  long-  lines  of  sewer  laid  beneath 
the  line  of  saturation  have  proved  to  be  practically  useless 
from  lack  of  a  proper  conception  of  the  influence  of  g-round 
water  and  lack  of  proper  methods  for  its  removal  or  exclu- 
sion from  the  sewers  proper. 

The  subject  of  subsoil  drainage  will  be  considered  more 
at  leng-th  in  a  subsequent  chapter. 


CHAPTER  III. 

THE  SEPARATE  SYSTEM. 

The  object  of  the  Separate  System  of  sewers  is  the  com- 
plete removal  of  the  sewag-e  proper  from  towns,  in  such  a 
manner  as  shall  best  subserve  the  convenience  and  health  of 
the  inhabitants. 

To  accomplish  this  object  in  the  most  satisfactory  man- 
ner, three  thing^s  are  required,  viz.:  constant  and  rapid  flow 
of  the  sewag-e,  thoroug"h  flushing",  and  adequate  ventilation. 

Whatever  tends  to  promote  either  of  these  three 
requirements  is  advantag^eous  to  the  system  and  should  be 
adopted.  We  will,  therefore,  consider  what  method  of  con- 
struction and  combination  of  appliances  will  best  attain  the 
end  in  view.  It  is  evident  that  to  increase  the  size  of  the 
sewers,  so  as  to  make  them  larg-e  enoug-h  to  carry  the  water 
of  occasional  storms,  would  be  detrimental  to  the  efficiency 
of  the  sewers,  inasmuch  as  the  ordinary  flow  would  be 
impeded  and  retarded,  and  thoroug-h  flushing-  and  ventilation 
made  more  difficult,  if  not  impossible. 

In  a  majority  of  cases  the  storm  water  can,  without 
causing  trouble,  run  in  the  surface  gutters  and  ditches  until 
it  reaches  the  natural  water  courses.  Only  in  larg-e  cities, 
where  the  water  would  need  to  run  long-  distances  throug-h 
the  streets,  would  any  underg-round  conduits  for  storm 
water  be  necessary.  Where  this  is  the  case,  either  the 
sewer  may  be  sufficiently  enlarg-ed  for  that  purpose,  or  a 
separate  channel  may  be  provided  for  the  storm  water.  The 
necessary  leng-th  of  these  storm  water  sewers  will,  in  any 
case,  be  but  a  small  fraction  of  the  whole  system. 


CHAP.  III.  THIC    SEPARATE   SYSTEM.  47 

Roof  Water. — On  the  other  hand,  if  the  introduction  of 
a  certain  amount  of  roof  water  into  the  sewers  will  insure 
their  thorough  flushing-  whenever  there  is  a  sufficient 
shower,  advantag-e  should  be  taken  of  such  ready  means  for 
accomplishing  so  desirable  an  end. 

The  object  being-  not  the  disposal  of  the  roof  water  but 
the  flushing-  of  the  sewers,  no  more  roof  water  should  be 
used  than  is  sufficient  for  that  purpose;  and  the  eng-ineer 
must  carefully  determine  at  what  points,  and  in  what  quan- 
tities, the  roof  water  may  be  introduced. 

Size  and  Material. — The  discussion  in  a  subsequent 
chapter  of  the  amount  of  sewag"e  per  capita  which  it  is  neces- 
sary to  provide  for,  and  the  carrying-  capacity  of  pipes,  will 
show  that  the  commonly  received  notions  concerning-  the 
required  size  of  sewers  are  entirely  erroneous. 

In  a  majority  of  cases  the  people's  money  is  spent  in 
building-  larg-e  sewers,  when  smaller  ones  would  be  more  effi- 
cient and  cost  very  much  less. 

Having  determined  the  amount  of  sewag-e  to  be  provided 
for,  and  the  size  of  conduit  necessary,  the  next  step  is  to 
determine  the  material  for  the  conduit.  Up  to  18  inches  in 
diameter  the  best  material  is  g-lazed,  vitrified,  earthenware. 
It  affords  a  smooth  surface  for  the  flow  of  the  sewag-e,  and  is 
durable  and  cheap.  Above  18  inches,  sewers  of  brick,  laid  in 
hydraulic  cement  are  preferable. 

Flushing. — While  the  problem  of  flushings  the  small 
sewers  of  the  Separate  System  is  a  much  less  difficult  one 
than  that  of  flushing-  the  larg-e  sewers  of  the  Combined  Sys- 
tem, still  the  matter  is  of  the  hig-hest  importance  and  should 
receive  the  careful  attention  of  the  eng-ineer.  Any  of  the 
methods  made  use  of  in  the  Combined  System  can  be  more 
easily  employed  in  the  Separate  System,  as  a  much  smaller 
quantity  of  water  is  required.  With  the  ordinary  flow  of 
sewag-e  in  the  pipes  a  fung-ous  g-rowth  appears  attached  to 
the  pipes  beneath  the  flow  line.     This  collects  the  sediment 


48  THE  se:parate  system  of  sewerage. 

and  slime  from  the  sewag'e  and  retards  the  flow.  Even  in 
pipes,  which  are  apparently  in  g^ood  condition,  a  careful 
examination  will  disclose  the  fact  that  the  surface  of  the  pipe 
under  the  sewag^e  is  foul,  and  rapidly  gfoing-  from  bad  to 
worse.  A  rush  of  water  will  detach  the  fung-ous  g-rowth, 
and  with  it  all  of  the  filth  which  it  has  collected,  and  will 
carry  it  on  to  the  out-fall. 

Let  any  one  examine  a  sewer  which  has  not  been  flushed 
for  several  days.  At  first  g"lance  he  will,  perhaps,  see  noth- 
ing" amiss.  All  seems  to  be  in  g"ood  order.  But  then  dis- 
chargee a  volume  of  water  into  the  sewer,  sufiicient  to  nearly 
fill  it  for  several  yards.  The  flakes  of  f  ung"ous  and  the  black 
shiny  clots  of  putrefying-  org-anic  matter,  which  will  be 
driven  along"  by  the  rush  of  water,  will  disclose  how  rapidly 
the  sewers  g"row  foul  with  a  quiet,  even  flow  of  sewag"e  in 
them,  and  how  essential  the  provision  for  frequent  and 
thoroug"h  flushing". 

If  the  rain  could  be  relied  upon  to  come  at  reg"ular  inter- 
vals, the  problem  of  flushing"  would  be  readily  solved.  All 
that  would  be  necessary,  would  be  to  provide  for  the  dis- 
charg"e  of  the  requisite  amount  of  roof  water  into  the  sewers. 
But,  unfortunately,  there  may  be  weeks  without  rain,  and 
during"  these  seasons  of  drouth  some  means  must  be 
employed  to  supply  the  lack  of  rain  water.  This  may  be 
done  in  several  ways.  A  flush  tank  mounted  on  wheels  can 
be  used,  and  this  is  available  in  towns  without  water  works. 
In  towns  provided  with  water  works  the  flushing"  can  be  done 
directly  from  the  water  pipes,  or  by  means  of  automatic 
flush  tanks. 

Ventilation. — The  ventilation  of  sewers  has  always  been 
a  difficult  problem  for  the  eng"ineer,  and  especially  is  this  the 
case  where  the  Combined  System  is  used.  In  the  Separate 
System,  properly  constructed,  and  where  ample  provision  is 
made  for  flushing",  the  problem  is  much  simplified.  If  only 
fresh,   running"  sewag"e  is  found  in  the  sewers,  and  there  is. 


CHAP.     III.  IHl';    SICPAKATIO    SYSTICM.  49 

no  place  where  the  sewag"e  can  stag"nate  and  decompose, 
there  will  be  verj'  little  sewer  g-as  developed.  If,  in  addition 
to  this,  the  sewers  are  reg'ularl}'^  and  thoroug-hly  flushed,  the 
air  in  the  sewers  will  be  so  frequently  chang-ed  that  there  is 
less  to  be  feared  from  them  on  account  of  sewer  gas,  even 
without  an}^  special  arrangement  for  ventilation,  than  from 
the  Combined  System  with  the  most  elaborate  appliances  for 
ventilation.  Besides  the  ventilation  secured  on  the  street 
lines  through  the  man-holes,  lamp-holes  and  flush-tanks,  a 
still  more  effective  means  of  ventilation  may  be  obtained  by 
carrying-  the  pipes  of  the  house  drains,  untrapped,  up  above 
the  roofs  of  the  houses. 

We  quote  the  following  from  Dr.  Alfred  Carpenter  in 
\\\Q.  Journal  of  the  Society  of  Arts: 

"If  a  sewer  flushes  clean,  as  it  ought  to  do;  if  it  does  not  become  the  habitat 
of  sewerage  confervoid  growths  upon  its  invert;  that  is,  if  it  is  regularly 
scoured  above,  as  well  as  below  the  line  at  which  the  sewage  ordinarily  runs;  if 
there  is  nothing  to  intercept  the  passage  of  sewage  from  its  origin  to  its  depart- 
ure at  the  outlet,  then  there  will  be  no  sewer  gas,  there  will  be  no  stink,  there 
will  be  no  danger  to  anybody. 

"The  openings  on  the  inverts  of  the  arch  of  the  street  sewer  will  be  inlets 
for  fresh  air,  and  the  ventilators  produced  by  the  extension  of  the  soil  pipe  of 
every  water-closet  above  the  level  of  the  house  top  will  be  outlets  for  the  air 
which  has  passed  through  the  sewer.  Thus  a  constant  circulation  will  be  pro- 
moted at  all  times  by  the  ordinary  laws  which  belong  to  gases,  and  which  by 
their  very  nature  prohibit  stagnation  in  fluids  of  all  kinds.  Occasionally  there 
may  be  down  draughts,  but  they  will  be  of  no  more  moment  than  the  down 
draughts  through  an  ordinary  chimney—  indeed  they  will  be  as  infrequent  as  a 
down  draught  into  a  furnace  when  the  fire  is  low.  Fresh  sewage  is  not  danger- 
ous to  anybody,  but  if  it  is  kept  within  the  curtilage  of  the  dwelling  house  by 
means  of  interceptors,  or  if  it  be  allowed  to  stagnate  in  a  badly  constructed 
sewer  until  fermentative  changes  have  arisen  within  its  substance,  it  then  pro- 
duces the  chance  of  evil;  but  in  the  present  day  no  authority  ought  to  be 
allowed  to  keep  sewage  within  its  borders  until  such  a  change  has  taken  place. 
It  should  be  "moved  on"  out  of  range  as  rapidly  as  possible.  The  house  is  the 
unit  of  sanitary  work,  and  it  is  wrong  for  selfishness  to  assert  itself  so  as  to 
determine  that  no  man  shall  assist  the  local  authority  in  its  duty  to  provide  for 
sewer  ventilation. 


50  THIC    SICPAKAIK    SYSTKM    Ol"    SKWIOKAGK. 


"I  utterly  object  to  the  principle  which  is  being  tried  to  be  established  by 
various  supposed  authorities,  viz.;  that  the  duties  of  the  individual  are  antago- 
nistic to  the  duties  of  the  local  authority  in  the  matter  of  sewers.  If  each  unit 
does  his  part,  the  duty  of  the  local  authority  as  to  ventilation  is  simple.  The 
latter  has  to  convey  away  the  sewage,  and  provide  inlets  for  fresh  air.  The 
outlets  must  be  at  the  highest  points,  and  if  they  are  so  placed,  there  will  not 
be  a  particle  of  danger  from  the  production  of  sewer  gas.  An  authority  has  an 
important  duty  to  perform,  viz.:  to  prevent  the  production  of  sewer  air,  as  a 
major  part  of  its  work.  The  provision  for  its  escape,  if  it  does  accidentally 
form,  will  be  best  met  by  details  in  the  construction  of  the  house  drain.  Con- 
centration should  not  take  place,  and  without  concentration  sewer  gas  is  per- 
fectly harmless.  There  will  be  no  diffusion  of  eathetic  germs,  for  they  cannot 
live  in  fresh  air  long  enough  to  spread  infective  disease,  and  if,  perchance,  a 
few  should  be  discharged  in  the  higher  regions  above  the  heads  of  a  great  or 
small  community,  they  die  in  a  very  few  seconds 

"The  germs  which  produce  enthetic  disease  cannot  live  in  fresh  air,  an\  more 
than  a  fish  can  live  in  unaerated  water.  If  discharged,  they  should  be  diffused 
above  the  heads  of  the  people,  and  not  at  the  street  level.  These  are  my 
reasons  for  advocating  the  extension  of  every  soil  pipe,  so  that  each  water  closet 
has  a  ventilator  in  action,  and  by  this  means  properly  constructed  sewers  will 
admit  fresh  air  at  the  street  level;  and  under  common  conditions,  foul  air,  if 
produced,  will  escape,  where  it  will  fail  to  set  up  even  the  smallest  possible 
danger.  I  advocated  this  principle  twenty  years  ago,  and  experience,  since  my 
first  paper  upon  this  subject,  has  imply  proved  that  I  am  right." 

There  are  two  methods  of  carrying-  out  the  plan  advo- 
cated by  Dr.  Carpenter.  One  is  by  carrying-  the  soil  pipes 
up  throug-h  the  house  so  that  they  may  serve  also  as  venti- 
lating^ pipes,  and  the  other  is  b}'  carrying-  a  separate  venti- 
lating- pipe  up  on  the  outside  of  the  house.  Both  of  these 
plans  will  be  considered  in  detail  in  a  subsequent  chapter. 

Special  Features. — The  Separate  System  of  sewerag-e  is 
not  new  and  untried.  It  has  been  advocated  by  sanitary 
eng-ineers  for  nearly  half  a  centur}',  and  the  arg-uments  for 
its  adoption  have  been  presented  in  many  forms.  It  was 
lirst  used  in  Eng-land.  It  is  in  successful  operation  in  many 
towns  in  the  United  States,  and  is  rapidly  g-rowing-  in  popu- 
laritv  as  it  is  better  known  and  understood. 


CHAP.     III.  rillO    SKFAKA'IIC    SYSTIOM.  ,>  1 

The  separation  of  sewagfe  proper  (house  sevvag-e)  from 
the  storm  water  falling-  on  pavements,  roofs,  areas  and  lawns 
has  been  much  more  complete  in  the  United  States  than  in 
Eng-land. 

The  plans  employed  in  the  diiferent  cities  where  it  has 
been  adopted  are  similar  in  g-eneral  design,  but  differ  in  the 
details.  The  different  conditions  met  with  in  the  different 
localities  would  require  a  certain  amount  of  variation,  and 
each  eng-ineer  has  followed  his  own  methods  for  solving-  the 
problems  which  presented  themselves.  The  following- 
examples  will  show  how  the  plans  vary  in  different  places: 

In  the  sewers  of  Memphis,  Tenn.,  desig-ned  by  Geo.  E. 
Waring-,  Jr.,  all  storm  water  was  excluded,  and  a  Field's 
flush  tank  was  placed  at  the  head  of  each  branch  sewer. 
The  sewers  are  ventilated  throug-h  the  uritrapped  interior 
house  drains  and  ventilating-  pipes.  Man-holes  were  g-ener- 
ally  omitted.  Drain  tile  was  laid  in  the  same  trench  with  the 
sewers. 

In  the  sewers  of  Pullman,  111.,  desig-ned  by  Benezette 
Williams,  C.  E.,  the  sewers  are  flushed  by  connections  with 
the  water  mains,  and  the  house  drains  are  flushed  b}^  auto- 
matic flushing  basins.  Man-holes  were  placed  160  feet  apart 
on  the  mains  and  200  feet  apart  on  the  laterals. 

In  the  sewers  of  Bing-hampton,  N.  Y.,  desig-ned  bv 
Rudolph  Hering-,  roof  water  is  used  for  flushing-,  and  in  part 
of  the  system  the  sewers  are  made  larg-e  enoug-h  to  carry  the 
storm  water. 

The  details  of  the  plan  adopted  for  the  sewers  of  Sche- 
nectady, N.  Y.,  and  the  methods  employed  in  their  construc- 
tion are  similar  to  those  described  in  the  subsequent  chap- 
ters.    A  Van  Vranken  flush  tank  is  placed  at  each  dead  end. 

The  sewers  of  West  Troy,  N.  Y.,  are  mainly  the  Sepa- 
rate System.  Certain  portions  of  the  city,  however,  are 
relieved  from  storm  water  throug-h  main  sewers,  which  also 
serve  as  mains  for  the  Separate  System.     Certain  portions  of 


52  THE    SEPAKATK    SYS  T  KM    OF    SEWERAGE. 

the  city  where  the  volume  of  ground  water  was  larg-e  are 
also  relieved  by  tile  drains.  These  are  ordinarily  laid  paral- 
lel with  the  sewers  in  the  same  trench  and  in  most  cases  dis- 
charg"e  into  rnan-holes.* 

In  the  city  of  Dayton,  Ohio,  the  sewers  are  mainly  on  the 
Separate  System  as  shown  by  the  map  on  a  subsequent  pag-e. 
The  storm  water  is  removed  mainly  throug-h  surface  g"ut- 
ters.  In  some  cases,  however,  there  are  underg-round  con- 
duits. 

The  sewers  of  the  Separate  System  in  Dayton  var}^  from 
forty-two  inches  in  diameter  to  eig-ht  inches  in  diameter. 
Man-holes  are  placed  at  all  junctions  and  on  long-  blocks  one 
is  usually  placed  midway.  All  dead  ends  are  provided  with 
automatic  flush  tanks. 

A  considerable  portion  of  the  city  was  formerly  subject 
to  overflow  from  which  it  is  now  protected  by  a  levee.  The 
entire  system  of  sewers  on  the  east  side  of  the  Miami  river 
converge  at  a  point  near  the  levee  at  which  there  is  a  pump- 
ing- station  of  a  capacity  of  about  twenty  million  g-allons  per 
day.  The  sewag-e  is  at  present  discharg-ed  into  the  Aliami 
river.  The  pumping-  station,  however,  commands  consider- 
able area  of  low  lying-  land  which,  should  future  conditions 
dictate,  can  be  utilized  as  a  sewag-e  farm. 

It  is  evident  that  the  Separate  System  is  especially  appli- 
cable where,  for  any  reason,  sewag-e  must  be  pumped;  or 
where  it  is  to  be  purified  by  any  of  the  many  processes  for 
that  purpose;  or  where  the  sewag-e  is  utilized  on  a  sewag-e 
farm.  In  all  of  these  cases  the  exclusion  of  the  storm  water 
from  the  sewag-e  g-reatly  reduces  the  attendant  expense  of 
the  process. 

Among  the  many  advantag-es  in  favor  of  the  Separate 
System,  the  one  which  appeals  most  strong-ly  to  the  averag-e 
citizen  is  that  of  reduced  cost.  This  is  the  arg-ument  which 
reaches  the  heart — t)r,  what  is  quite  as  necessary,  the  pocket 


See  map  of  West  Troy. 


CHAP.    III.  THIO    S1-:PAKAT1';    SVS'lIOM.  58 


— of  the  tax-payer.  One  of  the  grave  objections  to  the  Com- 
bined System  is  its  cost.  The  actual  cost  of  such  systems 
has  been  from  S2.O0  to  SIO.OO  per  foot.  The  cost  of  the  Sep- 
arate System  has  varied  from  75  cents  to  $2.00  per  foot.  It 
is"  safe  to  say  that  under  ordinary  circumstances  its  cost  will 
be  from  one-eig"hth  to  one-third  of  that  of  the  Combined 
System. 

It  may  be  asked  why  the  Combined  System  is  still 
adopted  in  so  many  cases,  if  the  advantag"es  of  the  Separate 
System  are  so  apparent.  The  answer  to  that  question  is, 
that  engineering-  precedent  carries  g-reat  weight  with  it 
among-  eng"ineers,  and  a  venerable  error,  even,  is  hard  to  put 
down.  The  Combined  System  is  one  of  natural  growth.  In 
cities  the  natural  water  courses  are  covered  over  and  con- 
verted into  sewers,  and  branches  are  built  leading  into  them. 
Then  the  branches  are  extended,  until  they  form  a  complete 
system  of  sewers. 

You  can  see  the  beginning  of  this  system  in  almost  any 
town  which  has  a  small  creek  running  through  it.  The 
creek  will  be  parth'  arched  over,  and  branch  drains  will  be 
constructed  leading-  into  it,  long-  before  the  subject  of  sewers 
is  brought  up  for  consideration.  When  the  matter  does 
come  up,  the  chances  are  that  the  system  already  beg-un  is 
simply  extended  and  completed,  and  another  bad  precedent 
is  set,  which  makes  the  introduction  of  the  better  system 
more  difficult. 

Although  local  conditions  and  considerations  of  economy 
may  in  some  cases  make  it  the  part  of  wisdom  to  combine 
storm  water  and  house  wastes  in  the  same  conduits  for 
removal,  the  attainment  of  perfect  house  drainag-e  cannot  be 
furthered  by  so  doing-,  and  quite  likely  will  be  jeopardized. 
Nothing-  interfering-  with  the  utmost  attainable  perfection  in 
the  sanitary  condition  of  the  drains  connected  with  the  inte- 
rior of  our  dwellings  should  be  allowed.  If  sub-surface  con- 
duits for  other  purposes  than  house    drainage,  and  not   so 


54  THIC    SKPARATK    SYSTKM    OK    SliWKHAGK. 

connected,  are  less  perfect  in  their  sanitary  condition  (and 
from  the  inconstant  nature  of  their  use  they  must  be),  it  is  a 
matter  of  less  importance;  since  opening-  into  an  unconfined 
and  widely  circulating-  atmosphere,  any  noxious  g-ases  are  in 
so  much  g-reater  deg-ree  diluted  and  rendered  innocuous. 

The  introduction  of  the  Separate  System  marks  an  im- 
portant era  in  the  development  of  sanitary  drainage,  recog^- 
nizing-,  as  no  other  system  has,  the  prime  importance  of  an 
early  removal  of  household  and  industrial  wastes,  which  are 
the  main  factors  in  soil  pollution.  That  it  will  best  meet  the 
requirements  of  all  larg-e  and  densely  populated  cities  (econ- 
omy considered),  is  not  probable.  That,  under  competent 
advice,  it  can  meet  the  requirements  of  house  drainage  more 
perfectly  in  any  city  than  the  Combined  System,  cannot  be 
denied.  It  is  peculiarly  adapted  to  many  of  the  numerous 
smaller  cities,  which  have  been  practically  debarred  from 
sewerag-e  by  its  cost,  and  to  outlying-  portions  of  larg-er  ones. 
Its  comparatively  small  cost  permits  an  early  and  g-eneral 
extension,  and  the  removal  of  domestic  wastes  before  the 
soil  has  become  saturated  with  them  beyond  a  reasonable 
hope  of  iiuritication. 

The  wid^  application  which  can  be  made  of  this  system 
will  be  apparent  upon  an  examination  of  the  following-  classi- 
fication of  the  cities  and  towns  of  the  United  States.  The 
table  classifies  all  the  cities  and  towns  of  the  United  States 
of  S,()()0  inhabitants  and  upward  by  the  number  of  inhabi- 
tants as  g-iven  in  the  census  of  18*.»0.  The  census  returns 
also  illustrate  the  increasing-  tendency  toward  the  ag-g-reg-a- 
tion  of  population  in  cities  where  sanitary  works  are  imper- 
ative. 

"In  the  published  records  of  former  censuses  urban  population  has  been 
defined  as  that  element  living  in  cities,  or  other  closely  aggregated  bodies  of 
poptilation.  containing  8,000  inhabitants  or  more.  This  definition  of  the  urban 
element,  although  a  somewhat  arbitrary  one,  is  used  in  the  present  discussion 
of  the  results  of  the  Eleventh  Census  in  order  that  they  may  be  compared 
directly  with  those  of  earlier  censuses.      The  limit  of  8,000  inhabitants  is,  how- 


CHAP.  III. 


'PHio  sioPAKA'iic  systi:m. 


ever,  a  high  one,  inasmuch  as  most  of  the  distinctive  features  of  urban  life  are 
found  in  smaller  bodies  of  population.  Recognizing  this  fact,  the  discussion  of 
the  urban  class  was  in  1880  extended  in  part  to  include  all  such  bodies  of  pop- 
ulation down  to  a  limit  of  4,000,  a  precedent  which  will  be  followed  in  the 
more  extended  publications  of  the  Eleventh  Census 

"According  to  this  definition  the  urban  population  of  the  country  in  1890 
was  18,235,670,  the  total  population  being  62,622,250.  The  urban  population 
constituted  in  1890,  29.12  per  cent,  of  the  total  population.  Corresponding  fig- 
ures for  the  several  censuses  are  given  in  the  table  opposite. 

"It  will  be  seen  that  the  proportion  of  urban  population  has  increased 
gradually  during  the  past  century  from  3.35  up  to  29.12  per  cent.,  or  from  one- 
thirtieth  up  to  nearly  one-third  of  the  total  population.  The  increase  has  been 
quite  regular  from  the  beginning  up  to  1880,  while  from  1880  to  1890  it  has 
made  a  leap  from  22.57  up  to  29.12  per  cent.,  thus  illustrating  in  a  forcible 
manner  the  accelerated  tendency  of  our  population  toward  urban  life." 

TABLE  I. 

I'RB.AN  POPULATION"  OF  THE  UNITED  ST.^TES. 


CENSUS  YEARS. 


1790 

1800. 

1810. 

1820. 

1830 

1840. 

1850 

i860. 

1870. 

1880. 

1890. 


Population 

of  the 

United  States 


3,929,214 

5,308,483 

7,239,881 

9,633,822 

12,866,020 

17.069  453 

23  191,876 

31,443.321 

38.558.371 
50,155.783 
62,622,250 


Population 
of  cities 


131.472 
210,873 
356,920 

475.135 
864,509 

1. 453.994 
2,897,586 
5,072,256 
8,071,875 
11,318,547 
18,235,670 


Inhabitants  of 

cities  in  each 

100  of  the  total 

population. 


3  35 

3  97 
493 

4  93 
6.72 
8.52 

12  49 
16.13 
2093 
22.57 
29.12 


56 


'l'Hl<:    SI2PAKATK    SYSTIiM    OF    SEWKRAGE. 


"The  following  table  shows  the   number  of  cities  classified  according   to 
population  at  the  date  of  each  census. 

TABLE   II. 

CITIES    CLASSIFIED    ACCORDING    TO    POPULATION. 


a 
> 

3 

a 

O 

d 

n 

0 
H 

12,000 

to 
20,000. 

0"  d 

I 

40,000 

to 
75,000. 

0   d 
80  o_ 

'loo 

250,000 

to 
500,000. 

0   d 

0 

1790   . 
1800. . 

6 

I 

3 

I 

6 

I 

3 

I 

I81O 

4 
3 

12 

2 

3 
2 

2 

1820 

13 
26 

4 

7 

1 1 

2 

2 

1830. . 
1840.  . 
1850. . 

3 
10 

I 

I 

2 

* 

44 

85 

17 
36 

I 

3 
3 

I 

I 

20 

14 

7 

3 

I 

r 

i860. . 

141 

62 

34 

23 

12 

2 

5 

I 

2 

1870. . 

226 

92 

63 

39 

14 

8 

3 

5 

2 

1880. . 

286 

1 10 

76 

55 

21 

9 

7 

4 

3 

I 

1890.  . 

443 

173 

105 

91 

35 

14 

14 

7 

I 

3 

According'  to  the  census  of  1880  about  seven-eig^hths  of 
the  cities  of  the  United  States  C^OT)  had  less  than  25,000 
inhabitants.  It  is  probable  that  most  cities  of  less  than 
4,000  inhabitants,  and  many  that  have  8,000  inhabitants  do 
not  require  an  extensive  system  of  sub-surface  removal  for 
storm  water,  and  that  in  the  fev^^  remaining-  the  sj^stem  of 
conduits  for  sub-surface  removal  may  be  very  limited. 

It  is  also  probable  that  a  ver}'  small  percentag'e  of  these 
cities  of  less  than  8,000  inhabitants  have  a  comprehensive 
plan  of  sewag^e  for  the  removal  of  house  wastes.     The  g^reat 


CHAP.   III.  THIO    SICPAKATl-;    SYSTIOM.  .)  ( 

majority  of  them  are  doubtless  expending-  what  little  capital 
they  devote  to  this  end,  both  public  and  private  funds,  in  a 
wav  that  will  not  contribute,  ultimately,  toward  a  harmoni- 
ous system  and  consequently  to  a  g^reat  extent  wastefully. 

In  view  of  these  facts  and  the  statistics  of  the  census 
bureau  quoted,  it  becomes  apparent  that  the  Separate  Sys- 
tem of  se^verag■e  must  be  widelv  extended. 


CHAPTER  IV. 

PLANS. 

In  desig-ning  a  system  of  sewers  for  a  town,  there  are 
several  thing's  to  be  taken  into  consideration  before  deciding- 
upon  the  plan  to  be  adopted.  The  principal  points  to  be 
considered  are:  the  size  of  the  town,  its  situation  with  refer- 
ence to  the  disposal  of  sewage,  the  compactness  of  its  build- 
ings, its  topography,  its  water  supply-,  the  character  of  the 
soil,  the  sanitary  habits  of  its  citizens,  and  its  financial  con- 
dition. 

The  amount  of  sewage  in  any  town  will  depend  upon  the 
number  of  its  inhabitants,  their  habits,  and  the  abundance 
and  convenience  of  the  water  supply.  In  a  town  without  a 
public  water  supply,  the  amount  of  sewag"e  per  head  will  be 
much  less  than  where  water  is  abundant.  With  the  intro- 
duction of  water  works  comes  the  multiplication  of  water 
closets,  and  a  rapid  increase  in  the  use  of  water  for  baths 
and  various  household  purposes,  and  the  amount  of  sewage 
will  rapidly  increase.  The  volume  of  sewage  to  be  provided 
for,  in  any  case,  maA'  safely  be  taken  to  be  equal  to  the  vol- 
ume of  water  used. 

Sewage  Disposal. — The  disposal  of  sewage  is  a  problem 
of  the  highest  importance.  When  sufficient  fall  can  be 
obtained,  the  sewage  is  usually  carried  by  gravity  to  the 
nearest  stream,  or  large  body  of  water.  The  effect  of  sew- 
age pollution  on  streams  and  lakes  is  a  question  which  is 
rapidly  growing  in  importance  as  our  population  grtnvs  more 
dense,  and  more  towns  are  sewered. 

In  the  older  countries  of  Europe  the  pollution  of  water 
courses   by  sewag^e  has   forced   itself  upon  the  attention  of 


CHAP.  IV.  PLANS.  ,5i» 

g-overnment  officials,  and  string-ent  laws  have  been  passed  to 
protect  the  purity  of  streams.  In  this  country  the  time  is 
not  far  distant  when  the  pollution  of  streams  and  lakes  bv 
sewage  will  need  to  be  forbidden  by  law,  or  in  many  localities 
pure  drinking-  water,  in  any  considerable  quantities,  will  not 
be  obtainable. 

The  State  of  Massachusetts,  some  years  since,  took 
steps  in  this  direction  throug-h  "An  act  to  protect  the  puritv 
of  inland  waters."  Several  other  states  have  followed  with 
like  enactments. 

In  many  cases  there  is  no  available  out-fall  for  the  sew- 
ag-e,  and  the  question  of  its  disposal  comes  up  at  once  with 
the  inception  of  sewer  projects. 

The  methods  for  purifying-  sewag-e  by  chemical  pro- 
cesses are  many  and  various.  The  object  of  these  processes 
is  to  so  purify  the  sewag-e  that  the  water  may  be  turned  into 
the  streams.  The  residuum  is  used  as  a  fertilizer  and  for 
v^arious  other  purposes  but  is  practically  valueless  in  its 
crude  state.  Wherever  the  rig-ht  kind  of  land  is  available, 
the  sewag-e  may  be  used  for  irrig-ating^  crops,  and  this  has 
been  successfully  done  in  manv  cases. 

Sometimes  a  town  site  is  so  flat  that  sufficient  fall  cannot 
be  obtained  to  carry  off  the  sewag-e.  In  this  case  the  sewag-e 
may  be  pumped,  or  raised  by  Shone's  System. 

Storm  Water. — In  towns  where  the  houses  are  at  con- 
siderable distances  apart,  and  no  very  larj^e  proportion  of  the 
surface  is  paved,  the  storm  water  will  usually  be  easily  dis- 
posed of  without  providing-  any  underg-round  channels  for  it. 
But  in  larg-e  cities  compactly  built,  where  the  g-reater  part  of 
the  surface  is  paved,  and  where  the  water  would  need  to  run 
in  the  streets  for  long-  distances  to  reach  an  out-fall,  provis- 
ion must  be  made  for  the  storm  water.  This  may  be  done 
by  enlarg-ing^  part  of  the  sewers  so  as  to  carry  the  surface 
water  as  well  as  the  sewag-e,  or  by  constructing-  special  con- 


60  THK   SEPARATE    SYSTEM    OF    SlCWIiRAGP:. 

duits  for  the  surface  water.  These  special  conduits  may,  in 
most  cases,  be  very  much  shorter  than  the  sewers,  as  the 
storm  water  can  be  delivered  into  any  natural  water  course 
within  the  town,  while  the  sewag"e  must  be  carried  entirely 
out  of  the  town.  In  every  town  problems  will  arise  peculiar 
to  the  circumstances  in  each  case;  and  the  details  of  the  plan 
best  adapted  to  any  g^iven  requirements  must  be  worked  out 
to  suit  the  conditions  of  that  special  case. 

The  Preliminary  Survey. — Before  any  definite  plans  can 
be  determined  upon,  a  careful  topog"raphical  survey  must  be 
made.  A  study  of  a  reliable  map  of  a  town,  with  the  heights 
of  the  street  corners  and  points  at  changes  of  slope  noted 
on  it — or,  better  still,  with  the  contour  lines  drawn  on  it — 
will  enable  the  engineer  to  determine  approximately  what 
g-rades  are  available  for  the  sewers;  the  best  lines  for  the 
mains;  and  will  enable  him  to  so  desig^n  the  laterals  as  to 
lead  the  sewag^e  by  the  most  direct  route  to  the  out-fall. 

These  approximate  calculations  can  then  be  tested  by 
final  computations  made  from  the  diagram  in  Chapter  VI. 
If  there  are  any  defects  in  the  assumptions  of  inclination 
made,  it  will  become  apparent  from  the  diag"ram  when  the 
sizes  are  determined,  and  proper  corrections  can  then  be 
made. 

It  must  not  be  forg-otten  in  determining-  the  g^rades  to  be 
adopted,  that  a  continuous  rise  along-  the  crown  of  the  sewer 
is  required  for  the  upward  passage  of  air-currents,  as  well  as 
a  continuous  descent  along-  the  invert  for  the  downward  flow 
of  sewag-e.  To  accomplish  this,  it  is  necessar\^  when  the 
sewers  flowing"  into  a  man-hole  are  smaller  than  the  outflow- 
ing- sewers  to  which  they  are  tributary,  to  raise  the  crowns 
of  the  former  slig-htly  above  that  of  the  latter.  This  fre- 
quently occasions  a  considerable  loss  of  grade.  For  exam- 
ple, if  a  man-hole  having-  an  eig-hteen  inch  outlet  has  a  twelve 
inch  and  a  ten  inch  sewer  tributar}',  and  to  insure  a  free 


CHAP.   IV.  PLANS.  61 

deliver}^  at  all  times  we  raise  their  crowns  an  inch  above  the 
crown  of  the  outlet,  tfie  invert  of  the  twelve  inch  pipe  will  be 
raised  above  the  gfrade  line  seven  inches  and  that  of  the  ten 
inch  pipe  nine  inches.  This  is  illustrated  in  the  drawing-  of 
a  man-hole,  Plate  V.  Another  reason  for  raising-  the  inverts 
of  inflowing  pipes  at  man-holes,  is,  that  obstructions  are 
more  likely  to  occur  at  man-holes  than  when  the  sewer  has 
its  full  circular  section,  and  the  increased  descent  thus 
secured  tends  to  prevent  deposits. 

A  preliminary  survey  for  sewers  should  include  such 
measurements  as  will  enable  the  engineer  to  make  a  map  of 
the  town  and  profiles  of  the  streets.  The  lengths  and  direc- 
tions of  the  street  lines  should  be  carefullv  measured,  and 
levels  should  be  taken  at  every  one  hundred  feet  and  at  every 
change  of  slope  of  the  surface.  A  datum  should  be  selected 
and  its  distance  below  some  well  known  fixed  point  in  the 
town  be  given.  Bench  marks  for  levels,  and  reference 
points  for  line  should  be  established  at  everv  street  intersec- 
tion. 

The  establishment  of  bench  marks  should  be  the  first 
xstep  in  taking  the  levels,  and  it  should  be  done  independ- 
ently of  the  surface  levels,  as  extreme  accuracy  in  the  final 
location  of  the  g-rade  line  in  construction  is  necessarv  in 
order  that  portions  of  the  S3^stem  which  may  be  constructed 
separately  may  be  properh'  joined.  After  the  terrilor}'  is 
covered  with  a  proper  S3'stem  of  bench  marks,  which  have 
been  carefully  checked  by  cross  lines  and  found  to  be  cor- 
rect, the  surface  levels  can  be  taken  very  rapidlv  and  with 
less  care,  as  any  error  is  not  carried  but  is  eliminated  at  the 
succeeding  bench  mark. 

The  transit  and  level  notes  of  the  preliminarv  survey 
should  be  carefully  preserved,  after  they  have  served  their 
purpose  in  the  preliminary  work,  as  they  will  serve  as  a 
check  on  the  succeedinsf  work. 


62  TH1<:    SEPAKATIC    SYSTEM    OF    SP:WKRAGK. 

From  these  notes  a  map  can  be  made  and  the  contour 
lines  drawn  on  it  (as  in  the  maps  shown  in  front  of  book),  or, 
the  heig"ht  of  a  suflicient  number  of  stations  marked  on  it. 

The  surve}'  should  also  include  outlying-  portions  of  the 
territory  which  may  belong  to  the  same  natural  drainage 
basin,  and  for  the  storm  water  of  which  it  may  be  necessary 
to  provide  special  conduits.  Rough  profiles  of  the  streets 
can  now  be  made,  and  the  grade  lines  of  the  sewers  laid 
down  on  the  profiles.  The  method  of  determining  the 
proper  grades  is  fully  described  in  the  following  pages,  as 
also  the  method  of  determining  the  loss  of  elevation  on 
curves  and  in  the  case  of  a  smaller  sewer  being  tributary-  to 
a  larger  one. 

Having  located  the  out-fall  of  the  sewers  and  established 
its  height,  it  will  be  best,  in  determining  the  grades,  to  work 
from  the  out-fall  along  the  mains  to  the  laterals,  as  this  will 
show  the  height  at  which  each  junction  must  be,  and  what 
fall  is  available. 

Capacity  Required. — In  designing  a  system  of  sewerage, 
the  final  question  to  be  decided,  and  the  most  important  one, 
is  the  question  of  size. 

It  is  obvious  that  proportioning  a  plant  to  meet  the 
demands  of  so  inconstant  and  widely  varying  a  use  as  the 
removal  of  storm  water,  presents  especial  difficulties,  both 
as  to  economy  and  efficiency,  and  that,  g'enerally  speaking, 
the  possibilities  of  economical  construction  and  service  are 
measured  by  the  regularity  of  the  work. 

The  aggreg'ate  yearly  discharge  of  house  drainag"e  from 
areas  fairly  built  up  is  in  excess  of  the  entire  volume  of 
storm  water  that  ordinarily  reaches  the  street  catch-basins. 
Yet  the  capacity  required  for  the  ample  service  of  house 
drainage  is,  approximately,  but  one-fortieth  of  that  required 
for,  or,  more  properly,  of  that  usually  given  to,  sewers  for 
the  removal  of  sewaofe  in  combination  with  storm  water  from 


\ 


CHAP.    I\'.  PLANS.  63 

streets,  g-ullies,  roofs,  paved  areas,  etc.  In  fact,  thoug-h  rep- 
resenting" ultimately  the  g"reater  amount  of  work  in  the  Com- 
bined System  of  sewers,  it  is  considered  unnecessary  to 
make  house  drainag"e  a  factor  in  computations  determining 
their  sizes.  (See  Adams'  "Sewers  and  Drains  for  Populous 
Districts,"  page  37.) 

It  has,  therefore,  not  been  customary  or  necessary,  in 
designing-  sewers  of  the  Combined  System,  to  investigate 
carefully  the  statistics  of  water  consumption,  either  as  to  its 
quantity  or  the  varying  rate  of  flow  at  which  it  finally 
reaches  the  sewers.  In  designing-  a  plant  for  the  discharge 
of  house  sewage  exclusively,  a  consideration  of  these  ques- 
tions becomes  of  prime  importance. 

Size  is  dependent  not  only  on  the  qiaiiiti/y  of  sewage  or 
of  water  consumed,  which  in  ordinary  cases  is  its  measure, 
but  upon  the  manner  in  which  the  water  is  used  and  the 
peculiar  habits  of  the  tributary  population.  A  manufactur- 
ing district  may  consume  and  deliver  to  the  sewers  its  entire 
quota,  amounting  to  several  hundred  gallons  per  diem,  per 
capita,  within  a  few  hours,  while  the  sewag"e  from  a  resi- 
dence district  may  be  distributed  over  the  twenty-four  hours 
at  a  nearly  uniform  rate. 

The  quantity  of  water  actually  used  is  but  a  small  per- 
centage of  that  wasted,  and  while  the  use  of  water  in  dwell- 
ings is  intermittent,  having  ordinarily  three  maxima,  the 
waste  of  water  is  more  nearly  constant,  being-  caused  b}" 
leaky  and  imperfect  fixtures  or  taps  purposely  left  open  to 
secure  fresh  water  or  to  prevent  freezing. 

Besides  the  daily  variations  in  sewage  flow,  there  are 
wide  variations  on  different  days  of  the  week,  due  to  the 
varying  daily  habits  of  the  people.  The  maximum  weekly 
flow  is  ordinarily  on  Monday.  Thus,  representing  the  aver- 
age daily  flow  by  100,  the  maximum  rate  of  flow  during  an 
average  day  may  be  150,  and  Monday  having  in  addition  to 
these  fluctuations  those  peculiar  to  itself,  may  have  a  maxi- 


64  THE  s1':pakati<;  systi<:m  oi~  sewkragk. 


mum  rate  of  flow  one-third  g-reater,  which  would  be  repre- 
sented by  200;  and  since  the  sewers  must  be  proportioned  to 
discharg-e  the  maximum  flow  occurring-  at  any  hour  during- 
the  week,  in  this  case  it  should  be  made  to  carry  twice  the 
averag-e  daily  flow. 

Changes  of  Temperature. — There  are  also  wide  varia- 
tions in  water  consumption  and  consequently  in  sewag-e  flow, 
due  to  climatic  differences  and  variations  in  temperature, 
which  are  usually  too  little  considered  in  proportioning-  the 
size  of  sewers,  and  particularly  of  main  sewers. 

In  a  majority  of  our  cities,  the  maximum  consumption  of 
water  occurs  during-  the  winter  months,  and  as  it  is  due  to 
water  taps  which  are  left  open  to  prevent  freezing-,  a  gfi'eater 
percentag-e  of  the  total  consumption  than  in  ordinary  cases 
reaches  the  sewers,  and  the  maximum  rate  of  water  con- 
sumption becomes  in  still  g-reater  deg-ree  the  maximum  rate 
of  sewag-e  flow.  The  secondary  maximum  of  water  con- 
sumption, occurring-  in  summer,  is  in  greater  deg-ree  used 
for  purposes  which  withdraw  it  from  the  sewers,  as  in  street 
and  lawn  sprinkling,  etc. 

It  is  during-  this  maximum  rate  of  flow,  occurring  in  the 
winter  months,  that  sewers  are  more  likely  to  be  subcharg-ed 
than  at  any  other  time,  and  it  should  be  carefully  considered 
in  proportioning-  the  sizes  of  pipes  in  the  S3^stem.  It  is  true 
that  it  is  the  result  of  a  waste  of  water,  which  is  perhaps 
extravag-ant,  and  which  it  mi^ht  be  better  economy  to  check 
than  to  remove  by  sewerage. 

Use  of  Water  Increasing. — It  is  also  true  that  the  per 
capita  consumption  and  waste  of  water  has  been  g-radually 
increasing-  up  to  the  present  time,  and  is  likely  to  reach  still 
hig-her  figures.  This  increased  demand  for  water  has  been 
met  by  pumping-  eng-ines  of  much  higher  duty,  and  by 
improvements  in  water  works  g-enerally,  which  enable  them 
to  furnish  water  to  the  consumer  at  lower  and  lower  rates 


CHAP.   IV.  PLANS.  65 

per  g-allon,  commensurate  with  the  increased  economy 
secured.  This  in  turn  encourag^es  the  use  of  water  from 
the  public  mains  for  motive  power,  as  the  running-  of  eleva- 
tors, motors,  etc.,  and  for  the  thousand  and  one  purposes  of 
lig-ht  manufacturing,  requiring-  the  use  of  power,  always 
ready,  and  costing-  nothing-  when  not  wanted.  Rapid  as  has 
been  the  development  of  water  supply-  systems  in  the  United 
States,  their  capacity  has  barely  kept  up  with  the  demands 
of  the  people. 

It  is  likely,  however,  that  recent  developments  in  the 
electrical  transmission  of  power  and  a  g-rowing-  tendency  to 
conserve  the  water  supply  by  more  rig-id  inspection  and  the 
g-eneral  use  of  water  meters,  will  tend  to  reduce  the  averag-e 
consumption  of  water  in  most  cases. 


CHAPTER  V. 

QUANTITY  OF  SEWAGE. 

Owing"  to  the  scarcity  and  incompleteness  of  data  at 
present  accessible  on  the  actual  flow  of  sewers,  and  to  their 
unreliability  as  well,  and  to  the  very  complete  records  of 
water  consumption,  which  are  made  possible  by  the  use  of 
pumping-  machinery,  automatically  recording-  its  own  per- 
formances, an  investigation  and  classification  of  the  statis- 
tics of  water  consumption  will,  undoubtedly,  be  of  use  in 
designing  a  sewerage  system.  Size  is  entirely  a  matter  of 
calculation  from  data,  mainly  assumed,  as: 

(1)  The  extent  of  the  S3'stem. 

(2)  The  density  of  population,  or  the  probable  density 
of  population  in  the  near  future. 

(3)  The  number  of  gallons  of  sewerage  per  diem  per 
capita. 

(4)  The  varying  rates  of  sewage  discharge. 

(5)  The  inclination  of  the  sewers. 

(6)  The  smoothness  of  the  interior  surfaces  of  the 
sewers. 

Of  the  above  factors  entering  into  calculations  deter- 
mining size,  those  of  extent  and  inclination  only  are  capable 
of  exact  determination.  And  since,  in  designing  a  s^'stem  of 
sewerage  for  American  towns,  the  element  of  future  growth 
must  be  considered,  not  only  by  increased  density  of  popula- 
tion, but  by  the  extension  of  the  suburbs,  thus  extending 
the  dead  ends,  and  practically  converting-  what  was  formerly 
a  lateral  into  a  main,  the  factor  of  extent  may  be  considered 
to  have  an  element  of  uncertainty. 


CHAP.   V.  QUANTITY    OK    SEWA(il-;.  f)7 

Upon  the  accuracy  of  the  assumption  made  by  the 
eng^ineer,  then,  in  regard  to  these  variable  factors  entering- 
so  largely  into  his  calculations,  will  the  efi&ciency  of  the  sys- 
tem mainly  depend. 

The  following"  statistics  of  water  consumption  are  given 
with  a  view  of  showing  what  may  be  a  proper  value,  for  each 
of  these  variable  factors  in  ordinary  cases.  They  have  been 
collected  from  various  sources,  and  a  summary  is  presented 
in  condensed  tabular  form,  convenient  for  reference.  A  few 
statistics  of  sewage  discharge  are  also  presented,  but  owing 
to  the  difficulties  previously  stated,  they  indicate  the  condi- 
tion of  sewage  flow  for  a  very  brief  period  only,  and  admit  of 
but  limited  application.  When  examined  in  connection  with 
the  statistics  of  water  consumption  they  are  of  increased 
interest. 

The  consumption  of  water  will  be  examined  in  the  fol- 
lowing manner: 

(1)  The  quantity  of  water  consumed. 

(2)  Monthly  variations. 

(3)  Daily  variations. 

(4)  Hourly  variations. 

(5)  Variations  due  to  extremes  of  temperature. 

(6)  Special  cases — as,  cities  using  water  larg-ely  in 
manufacturing,  brewing,  etc. 

In  the  following  tables  the  standard  of  comparison  taken 
is  the  average  per  diem  per  capita  consumption,  which  is, 
for  purposes  of  comparison,  assumed  at  100,  and  from  statis- 
tical data  the  per  cent,  comparison  is  made  by  computation, 
as  this  is  most  convenient  for  use. 

The  average  per  diem  per  capita  consumption  is  that 
most  readily  obtained,  especially  from  pumping  records 
of  the  smaller  cities  in  which  records  are  usually  less  per- 
fect, being  computed  from  automatic  counter  readings.  In 
many  records  of  pumping  works,  where  the  supply  is  com- 


68  THE    SEPAKATK    SVSTKM    OF    SKWERAGK. 

pared  with  the  population,  the  results  are  misleading-.  For 
instance:  in  the  smaller  cities  of  from  10,000  to  15,000  inhab- 
itants, while  the  per  diem  per  capita  consumption,  based  on 
the  total  population,  is  but  little  below  the  average,  the 
actual  per  diem  per  capita  consumption  for  each  person 
using  water  from  the  city  mains  must  be  greatly  above  the 
average,  as  the  proportionate  number  of  consumers  in  such 
cities  is  frequently  below  one-half,  and,  consequently,  the 
sewage  flow  in  proportion  to  the  actual  tributary  population 
is  disproportionately  large.  This  condition  is,  undoubtedly, 
owing  to  the  usual  laxity  of  cities  of  this  class  in  controlling 
the  use  of  water,  and  is  corrected  as  the  city  increases  in 
population  and  improves  in  its  conduct  of  municipal  affairs. 

The  water  statistics  of  larg-e  cities  are  often  misleading 
in  the  other  direction,  many  supplying  water  from  the  city 
mains  to  their  own  entire  population,  and  to  outlying  subur- 
ban districts  as  well,  which,  in  many  cases,  is  not  stated  in 
published  reports.  In  many  cases,  also,  the  per  capita'  con- 
sumption in  published  returns  is  based  upon  estimates  of 
population,  which  are  merely  guesses  and  may  be  wide  of 
the  mark. 

The  sewerage  of  every  city  presents  problems  for  solu- 
tion essentially  peculiar  to  itself,  and  these  must  be  carefully 
considered.  The  tables  here  given,  while  not  strictly  appli- 
cable to  certain  special  cases,  will,  nevertheless,  be  a  guide 
in  determining  their  requirements. 

The  Quantity  of  Water  Required. — The  following-  is  J. 
T.  Fanning's  estimate  for  American  cities:  * 

"In  American  cities  having  well  arranged  and  maintained  systems  of  water 
supply,  and  furnishing  good,  wholesome  water  for  domestic  use,  and  clean, 
soft  water  adapted  to  the  use  of  the  arts  and  for  mechanical  purposes,  the  aver- 
age consumption  is  found  to  be  approximately  as  follows; 

(a)  For  ordinary  domestic  use,  not  including  hose  use:  20  gallons  per 
capita  per  day. 


*From  J.  T.  FanninK's  Hydraulic  Eiij^ineering,  by  permission 


CHAP.   V,  QUANTITY    OK    SKWAGIO.  6i» 

{&)  For  private  stables,  including  carriage  washing,  when  reckoned  on  the 
basis  of  inhabitants;   3  gallons  per  capita  per  day. 

(f)  For  commercial  and  manufacturing  purposes;  5  to  15  gallons  per  cap- 
ita per  day. 

((/)  For  fountains,  drinking  and  ornamental;  3  to  10  gallons  per  capita 
per  day. 

[e)     For  fire  purposes;   i  to  10  gallons  per  capita  per  day. 

(/)  For  private  hose,  sprinkling  streets  and  yards;  10  gallons  per  capita 
per  day  during  the  four  driest  months  of  the  year. 

(g)  Waste,  to  prevent  freezing  of  water  in  service  pipes  and  house  fix- 
tures in  northern  cities;  10  gallons  per  capita  per  day  during  the  three  coldest 
months  of  the  year. 

{/i)  Waste,  by  leakage  of  fixtures  and  pipes,  and  use  for  Hushing  purposes; 
from  5  gallons  per  capita  per  day,  upward. 

"The  above  estimates  are  on  the  basis  of  the  total  population  of  munici- 
palities. 

"The  domestic  use  is  greatest  in  the  towns  and  cities,  and  in  the  portions 
of  the  towns  and  cities  having  the  greatest  wealth  and  refinement,  where  water  is 
appreciated  as  a  luxury  as  well  as  a  necessity,  and  this  is  true  of  the  yard 
sprinkling  and  ornamental  fountain  use,  and  the  private  stable  use.      *     *     * 

"The  general  introduction  of  public  water  works  on  the  constant  supply 
system,  with  liberal  pressure  in  the  mains  and  house  services,  throughout  the 
American  towns  and  cities  has  encouraged  its  liberal  use  in  the  households,  so 
that  it  is  believed  that  the  /egitiinute  and  economical  domestic  use  of  water  is  of 
greater  average  in  the  American  cities  than  in  the  cities  of  any  other  country. 
at  the  present  time,  avd  its  general  use  is  steadily  increasing." 

The  proportion  of  the  above  per  capita  per  day  supply 
naturally  reaching-  the  sewers  ma}^  be  summarized  as  fol- 
lows: 

(rt)     Domestic  use,        -----        -20  g-allons. 

{b)    .Stables,      ------  8  g-allons. 

(c)     Manufacturing",     -         -         -         -         5  to  15  g-allons. 

{d)    Fountains,  -         -         -         -         -    8  to  10  g-allons. 

{g)   Waste  in  winter,  .         -         -         -        10  g-allons. 

(h')    Flushing-,  -----     5  to  15  g-allons. 


Total  supply  reaching-  sewers,     +6  to  78  g-allons. 

In  the  report  of  the  Eng-ineer  Department  of  Washing-- 
ton,  D.  C,  for  18V>T,  Captain  Edward  Burr  makes  the  follow- 


70 


THK    SKPARATK    SYSTKM     OF    SKWKKAGK, 


ing"  estimate,   per  capita,  of  the  leg-itimate  requirements  of 
that  city: 

For  domestic  purposes,  -         -         -         -      30  g^allons. 

For  commercial  and  U.  S.  purposes,         -  30  g-allons. 

For  sprinkling-  (maximum)  -         -         -       15  g-allons. 


Total  maximum  leg-itimate  use, 
Add  for  waste,  not  deliberate  or  wilful. 


75  g-allons. 
25  g-allons. 


Total,  100  g-allons. 

The  actual  consumption  for  1897  was  164  gallons  per 
capita  for  the  entire  population,  including-  suburban  and 
rural  population  entirely  without  water  facilities. 

As  an  example  of  the  actual  quantity  of  water  needed  for 
domestic  purposes,  the  following-  statistics  of  consumption, 
determined  by  meter  measurements,  are  extracted  from  an 
article  on  "The  Consumption  and  Waste  of  Water,"  by  Dex- 
ter Brackett,  M.  Am.  Soc.  C.  E.,  in  the  transactions  of  the 
American  Society  of  Civil  Eng-ineers,  1895: 

TABLE   III. 

ACTUAL    CONSUMPTION    BY    METER. 


No. 

Gallons 

CITY. 

of 

Class  of  Houses. 

per 

Houses. 

capita. 

Boston 

31 

Highest  cost  apartment  houses 

59 

Boston 

46 

First  class  apartment  houses 

46 

Boston 

223 
39 

Moderate  class  apartment  houses 
Poorest  class  apartment  houses 

3^ 

16.6 

Boston 

Newton 

490 

Houses  supplied  with  modern  plumbing 

26.5 

Fall  River 

28 

The  most  expensive  houses  in  the  city 

25-5 

Fall  River 

Total  domestic  consumption 
Total  domestic  consumption 

12.3 
16.8 

Worcester  . 

CHAP.  V.  yuAN'nrv   of   sewagk.  71 

From  these,  and  other  statistics  g-iven  in  his  article,  Mr. 
Brackett  draws  the  following-  conclusions: 

(1)  The  quantity  needed  for  domestic  use  is  not  more 
than  3U  gallons  per  inhabitant. 

(2)  It  is  not  probable  that  the  actual  requirement  for 
mechanical  and  manufacturing  uses  at  present  exceeds  4-0  gal- 
lons per  capita  in  any  of  our  larg-e  cities. 

(3)  The  quantity  needed  for  public  use  is  not  more 
than  .")  gallons,  making  a  total  of  7.5  gallons  as  the  maximum 
quantity  needed  for  actual  use,  without  any  allowance  for 
w'aste. 

It  is  estimated  that  in  man}'  places  the  needless  and  wil- 
ful waste  of  water  is  from  50  per  cent,  to  7.5  per  cent,  of  the 
entire  supply. 

The  following  table  illustrates  the  increase  in  water  con- 
sumption in  several  cities  : 


72 


THI<:    SKPAKATK    SYSTICM     OI'    SKWKKAGK. 


TABLE   IV. 

SHOWING    CONSUMPTION    OF    WATER    IN    TWELVE    AMERICAN    CITIES. 
Based  upon  the  Total   Population, 


CITIES. 


Boston 

Brooklyn.  .  .  . 

Buffalo 

Chicago 

Cincinnati  .  . 
Cleveland.  . . 

Detroit 

Jersey  City . . 
Louisville. . . 
Philadelphia 
Washington  . 
Montreal. .  .  . 


Average  Daily  Supply  Per  Capita  in 
Gallons. 


1874* 


60 

58 
60 
84 
45 
45 
87 
86 

24 
58 

66 


18841 


no 

63 

151 

145 

76 

88 

120 

136 

64 

81 

165 


84 

66 

170 

123 

99 


175 


62 


145 


i897t 


265 
127 


r28 
130 


215 

164 


*J.  T.  Fanning's  Hydraulic  Engineering;, 
tj.  J.  R.  Croes'  Statistical  Tables.  iS«5. 
tDepartnient  Reports. 


The  following"  table  compiled  from  the  statistics  of  one 
hundred  and  seventy-six  American  cities,  illustrates  the  con- 
sumption of  water: 


CHAP.  V. 


yuANTi'iv   oi'   si;\VA(;i:. 


TABLE  V. 

SHOWING    PER    DIEM    PER    CAPITA    CONSUMPTION    OK    WATER    IN    ONE    H(JNDREl)    AND 
SEVENTY-SIX    AMERICAN    CITIES    IN     1884. 

Based  upon  the  Total   Population  Census  of  1880  * 


CITIES. 


NO. 


POPULATION. 


Average  Consump- 
tion of  water  per 
diem  per  capita. 


10,000  to  15.000 76 

15,000  to  20,000 6g 

20,000  to  25.000 71 

25,000  to  50,000 

50,000  to  75,000 

75,000  to  100,000 

100,000  to  250,000 

250,000  to  500,000 

500, 000  and  over 


.86 
.80 

95 
102 


92 


*  Compiled  from  J.  J.   R.  Croes'   Statistiral  Tables,   1885. 

The  above  tables,  thougfh  g-iving-  the  average  dailv  use, 
are  not  sufficient  to  predicate  an  assumption  of  sewag"e  dis- 
charge upon,  as  they  indicate  simply  averages  obtained  from 
widely  varying  rates  of  consumption.  As  previously  stated, 
each  day  has  a  maximum  rate  of  discharge,  and  there  are 
also  weekly  and  monthly  maxima,  varying-  according  to  the 
habits  of  people,  and  to  the  conditions  of  temperature,  etc., 
and  the  sewers  (we  are  considering-  the  Separate  System, 
which  has  no  capacity  of  storage)  must  be  proportioned  to 
discharge  their  contents  at  the  maximum  rate  at  which  they 
are  received. 


74 


THK    SKPARATE    SYSTKM    OF    SF:WKRAGE. 


Varying  Rates  of  ^A^ale^  Consumption. — There  are  two 
principal  maxima  of  water  consumption,  one  occurring"  during^ 
the  coldest  weather,  and  one  during-  the  warm  and  dr}- 
months  of  late  summer.  It  is  the  former  which  particularly 
influence  the  sewag^e  discharg^e,  being"  in  most  cases  the  max- 
imum rate  of  water  suppl}"  for  the  year,  and  nearly  its  entire 
volume  reaching-  the  sewer,  while  the  uses  to  which  water  is 
put  during"  the  warm  and  dry  weather  maximum,  diverts  it 
larg-ely  from  the  sewers. 

The  following  table  indicates  the  monthly  variations  in 
water  consumption  during  the  year  18S4,  in  several  Ameri- 
can cities,  covering  a  considerable  rang"e  of  latitude.  The 
computations  are  made  from  statistics  appearing  in  official 
reports  of  the  water  departments  of  the  various  cities,  and 
are  reduced  to  the  per  cent,  basis  in  terms  of  the  averag"e 
monthlv  consumption. 

TABLE   VI. 

ILLUSTRATING   MONTHLY  VARIATION   IN   CONSUMPTION  OF  WATER  IN    1884.    IN  WHICH 
THE  MEAN   MONTHLY  CONSUMPTION   FOR  EACH  CITY  IS  REPRESENTED   BY    ICO 


CITIES. 

3 
C 
ct 

105 

138 

90 

88 
103 
III 
116 

u 
m 

D 
u 
XI 
lU 

bk 

107 
100 

77 
90 

79 

118 

96 

< 

102 

83 

90 

lOI 

83 

95 
79 

B 
S 

3; 
E 

D. 
a; 
X 

98 
100 
1 10 
113 
115 

95 
107 

..0 

2       > 
u         z 
Z       Z 

95      94 

91       87 

113     III 

no      92 

106,     97 

95      97 
100    104 

. 

Si 

E 

0 

Chicago 

Columbus 

New   Orleans.  . 
Cincinnati  .  .  . 
Wilmington  , .  . 

Buffalo 

Binghampton   . 

100 
107 

87 
89 
89 
114 
97 

100 

90 

105 

lOI 

77 
92 
90 

98 

93 

106 

106 

125 

96 

95 

lOI 

I  Of) 

113 

log 
120 

91 
98 

102 
1 12 
109 
114 
114 
96 
124 

96J 

95I 
96- 
86 
90 
99' 

From  the  above  table  we  find  the  average  maximum 
monthlv  consumption  forthe  seven  cities  to  be  119  H-7,  or, 
practically,  twenty  per  cent,  in  excess  of  the  average 
monthly  consumption. 


CHAP.  V 


QUANTITY     OI'^    SE\VA(;E. 


75 


The  daily  consumption  has  a  weekly  maximum  independ- 
ent of  atmospheric  conditions,  and  which  ordinarily  occurs 
on  Monday.  The  widest  variations  in  daily  consumption, 
however,  are  those  due  to  extremes  of  temperature. 

The  relative  minimum,  mean  and  maximum  daily  con- 
sumption, in  a  few  cases,  is  illustrated  in  the  following"  table 
in  terms  of  the  mean  daily  consumption.  The  computations 
are  based  upon  statistics  contained  in  official  reports. 

TABLE  VII. 

ILLUSTRATING    EXTREME    DAILY    VARIATIONS    IN    CONSUMPTION    OF    WATER    IN    1884, 
IN    WHICH    MEAN    DAILY    CONSUMPTION    IS    REPRESENTED    BY    lOO. 


CITIES. 

Minimum 
Daily  Con- 
sumption. 

Mean 
Daily  Con- 
sumption. 

Maximum  Daily 
Consumption 

Chicago 

Cincinnati 

Buffalo 

82 
60 
68 

100 
100 
100 
100 

120 
152 
140 
176 

DATE. 

Jan.     23 
June    24 
Feb.      5 
Jan.       1 

Columbus 

The  averag^e  maximum  daily  consumption  in  the  cities, 
g-iven  in  table  VII,  is  147,  or  forty-seven  per  cent,  in  excess 
of  the  mean  daily  consumption  of  the  year. 

The  average  maximum  daily  consumption,  given  above, 
indicates  only  averages  for  a  period  of  twenty-four  hours. 
It  will  be  necessary  to  ascertain  the  rate  of  the  heaviest 
hour's  use. 

The  following  table  indicates  hourly  consumption,  com- 
puted from  automatic  counter  readings  of  a  direct  service 
pumping  engine,  in  Kalamazoo,  Mich.: 


7t) 


THl-:    SliPAKATlO    SYSTKM    OF    SKWKKAGE. 


TABLE  VIII. 

HOURLY    VARIATIONS    IN    WATER    CONSUMPTION,     MONDAY,     MARCH    Q,     1886. 


TIME. 

Ciallons  per  Hour. 

TIME. 

Gallons  per  Hour. 

I    A.     M. 

52,528 

I    P.     M. 

58,520 

2 

49,964 

2        '  ' 

58,128 

3        " 

51.464 

3      " 

59.360 

4      " 

52,472 

4      " 

59,640 

5     " 

52,864 

5      " 

61,040 

6      •■ 

52,332 

6      " 

57,232 

7     ■' 

54,880 

7     " 

53.928 

8     " 

64  70S 

8      " 

56,560 

9     " 

62, 160 

9      " 

52,640 

10     " 

61,600 

10 

54,880 

II 

60,844 

II 

52,752 

12    M. 

61,964 

12      " 

48,328 

PERCENTAGE    RELATION. 

Average  hourly  rate loo 

Minimum      "        "    85.9 

Maximum     "        "    115. i 

If  this  table  be  examined  in  connection  with  Table  XII, 
showing'  sewer  g'aug'ing-s  taken  simultaneously  with  the 
counter  reading",  it  will  be  particularly  interesting".  A 
g'raphical  representation  of  the  two  on  the  same  sheet  shows 
almost  precisely  the  same  relative  variation  in  each. 

During  the  week  ending-  Aug^ust  20th,  18H3,  observations 
were  made  to  determine  the  rates  of  consumption  for  differ- 
ent portions  of  the  24  hours,  from  the  Mystic  works,  which 
supplied  a  population  of  117,000,  The  results  were  as  fol- 
lows: 


CHAP.   V. 


OUANTI'lY    OJ''    S)<:\VA(iK. 


TABLE  IX. 


Gallons  per  Capita 

Percentage  of 

per  Day. 

Average. 

I    A.    M.    to  4   A.    M. 

40  .s 

55 

4        "         t0  7        " 

58.6 

80 

7     "      to  lo   " 

103.8 

140 

lO     "         to   I    p.    M. 

930 

126 

I  P    M.   to  4       " 

93-2 

126 

4     "      to  7      ■  ■ 

79-5 

108 

7     "      to  lo   " 

61.9 

84 

lO     "         to    1    A.    M. 

52-9 

72 

Average 73  6 


The  following'  illustrations  and  estimates  of  varying-  con- 
sumption are  taken  from  J.  T.  Fanning-'s  Hydraulic  Engi- 
neering: 

"The  Brooklyn  diagram  shows  that  the  average  draught  in  the  month  of 
maximum  consumption  was  in  1872,  fifteen  per  cent,  in  excess  of  the  average 
annual  draught;  in  1873,  seventeen  per  cent,  in  excess;  in  1874,  thirteen  per 
cent    in  excess. 

"A  Boston  Highlands  direct  pumping  diagram,  lying  before  the  writer, 
shows  that  the  average  draught  at  9  o'clock  in  the  forenoon  was  thirty-seven 
per  cent,  in  excess  of  the  average  hourly  draught  for  three  months. 

"The  maximum  hourly  draught,  indicated  by  the  two  diagrams  taken 
together,  is  nearly  seventy-five  per  cent,  in  excess  of  the  average  throughout 
the  year. 

"In  illustration  we  will  assume  a  case  of  a  suburban  town,  requiring,  say, 
an  average  daily  consumption  for  the  year  of  1,000,000  United  States  gallons  of 
water,  and  compute  the  maximum  rate  of  draught  on  the  basis  shown  by  the 
above  named  diagrams,  thus: 


78 


THE    SJiPAUATK    SYSTICM    OF    SEWKKAGK. 


GALLONS. 

Average  draught  per  year           

1,000,000 
I,  170,000 
1,270,000 
1,640,000 
1,870,000 

Add    17    per    cent,     for    maximum     monthly    average 

draught,  making 

Add  to  the  last  quantity  10  per  cent,  for  the  maximum 

weekly  average  draught,  making 

Add  to  the  last  quantity  37  per  cent,    for  the  maximum 

hourly  average  draught,  making 

Add  to  the  last  quantity  23   per  cent,   for  the  maximum 

hourly  average  draught  on  Mondays,  making 

'  'The  maximum  hourly  draught  is  not  infrequently  one  hundred  per  cent,  in 
excess  during  several  consecutive  hours,  independent  of  the  occasional  heavy 
draughts  for  fires." 

Fanning-'s  estimate,  as  g^iven  above,  would  require  sew- 
ers capable  of  discharg-ing-  twice  the  mean  daily  water  con- 
sumption, upon  the  supposition  that  at  the  time  of  maximum 
consumption  its  entire  volume  reaches  the  sewers.  And 
this  being-  ordinarily  in  the  winter  months,  the  supposition 
is  a  reasonable  one. 

The  following  extracts  from  the  report  of  the  Louisville 
Water  Works  for  1890,  shows  the  relation  between  "con- 
sumption of  water  per  capita"  and  "consumption  per  each 
consumer"  from  1861  to  1889.    • 

It  appears  from  the  table  that  the  consumption  per  con- 
sumer has  been  without  any  notable  increase  previous  to  1880, 
since  when  there  has  been  a  considerable  increase.  During" 
this  period  the  consumption  per  capita  based  on  the  total 
J>0'pulaiion  has  increased  from  8.66  gallons  to  67.32  gallons: 


CHAP.   V. 


QUANTITY    OF    SKWAC.I-; 


79 


TABLE  X. 

WATER    CONSUMPTION    AT    LOUISVILLE.     KY. 


V 

u-c 

•—  i" 

0  ai 

0 

1)  . 

V  . 

0 

'X  Oi 

-2  = 

a'c 

« 

atn 

a, « 

1-.  " 

i"^ 

s  s 

"^  .— 

"7^ 

CO 

v° 

■^z 

Z  6 

0 

a. 

0 

.-"« 

-"a 

— 

Sfc-  P 

^!/i 

0 

CL,  j; 

a. 

xiC 

mO 

> 

1   " 

-^  0 

M  4) 

0. 
2.5 

-3  ^ 

a,  — 

a   1 
-  >- 

o.S 
0  1 

=< 

i= 

1^ 

.=  ■£ 

.§  ~ 

—  M 

0  « 

z 

zS 

0 

1'* 

U 

Ul 

a  " 

1889 

12,569 

12,262 

122,620 

132,400 

166,000 

67.32 

91.14 

1888 

11,698 

11,398 

113,980 

131,700 

165,000 

62.23 

77.96 

1  '887 

11,001 

10,729 

107,290 

131.000 

162,000 

63.62 

96.07 

1886 

10,243 

9.990 

99,900 

130,500 

160.000 

64.95 

104.02 

1885 

9,709 

9.469 

94,690 

130,000 

159.000 

62.39 

10477 

1884 

9,261 

9.034 

90,340 

125,500 

158,000 

56.22 

9833 

1883 

8,730 

8,594 

85,940 

125,000 

158,000 

51-91 

95-44 

1882 

8,293 

8,201 

82,010 

124,500 

157,000 

47.11 

go.  19 

I88I 

7.947 

7.877 

78,770 

124,000 

156,000 

55  47 

109.86 

1880 

7,506 

7.462 

74,620 

123,000 

i56,obo 

42.09 

88  01 

1879 

7-283 

7.243 

72.430 

123,000 

156,000 

33  16 

71.42 

1878 

7,012 

6.978 

69, 780 

120.000 

154,000 

29  35 

64-77 

1877 

6,820 

6,797 

67,970 

117.000 

154.000 

28.62 

64.65 

1876 

6.559 

6.541 

65.410 

116,000 

152,000 

27.44 

63-75 

1875 

6,234 

6,228 

62,280 

114,000 

152,000 

23.76 

57  98 

1874 

5.431 

5.591 

55.910 

109,000 

152,000 

23.68 

64.37 

1873 

4.742 

4.932 

49.320. 

98,000 

144,000 

22.32 

65.16 

1872 

4,268 

4.452 

44.520 

84,000 

136,000 

21.69 

66  25 

I87I 

3.911 

4.131 

41,310 

76,000 

129,000 

20. 86 

65-13 

1  1870 

3.436 

3,668 

36.680 

70,000 

122,000 

23.09 

79-53 

1869 

3.083 

3.312 

33,120 

64,000 

115,000 

21-53 

74.76 

1868 

2,695 

3,089 

30.000 

62.000 

109,000 

18.86 

66.30 

1867 

2,414 

2.783 

28,000 

60,000 

103,000 

18.24 

67.10 

IS66 

2,205 

2.434 

25,000 

56,000 

98  000 

18.87 

73.96 

1865 

1.766 

2,019 

20,190 

51,000 

92,000 

18.55 

85-35 

1864 

1.517 

1.754 

17.540 

49.000 

87,000 

14.27 

62.06 

1863 

1. 112 

1,300 

18,150 

40.000 

83.000 

11-43 

55-02 

1862 

794 

925 

13,000 

34,000 

78.000 

12. 98 

77.91 

I86I 

512 

582 

5,820 

32.000 

74,000 

8.66 

73  60 

80  THK   SP:PAKATK   system    Ol'^    SKWKKAGK. 


The  amount  of  sewage  to  be  provided  for  in  the  Sepa- 
rate System  is  an  important  question,  and  with  published 
statistics  showing-  a  variation  more  than  ten  fold  between 
maximum  and  minimum  in  water  consumption  for  different 
cities,  the  eng"ineer  who  essays  to  foretell  what  amount  will 
reach  the  sewers,  should  carefully  investig"ate  the  local  con- 
ditions. 

ScAA^er  Gaugings. — Exact  measurements  of  the  flow  of 
house  sewag-e  for  any  considerable  period  are  not  accessible, 
if  they  have  ever  been  made,  and,  consequently  we  cannot 
use  them  as  a  basis  in  determining  the  fluctuations  in  sewag"e 
flow,  or  the  ratio  of  maximum  to  mean  discharg-e. 

A  limited  number  of  g^aug^ings  have,  however,  been  made 
with  the  purpose  of  determining  the  maximum  rate  of  flow 
per  capita  in  certain  cases,  and  an  account  of  some  of  them 
appears  in  a  report  to  the  National  Board  of  Health,  by  G.  E. 
Waring,  Jr. 

The  most  complete  statistics  recorded  are  those  of 
gaugings  made  under  the  direction  of  Robert  Moore,  Esq., 
Civil  Engineer,  Commissioner  of  Sewers  of  St.  Louis.  The 
following  is  an  abstract  from  the  report: 

"The  sewer  drains  an  area  containing  1,370  houses,  occupied  by  a  popula- 
tion of  8,200.  The  total  number  of  water  taps  was  1,390.  The  diagrams  show 
gaugings  taken  every  hour  from  6  p.  m.  Monday,  March  15  to  eleven  a.  m., 
March  16,  and  from  8  a.  m.,  March  19.  to  8  a  m.,  March  23.  These  gaugings 
are  averaged  to  make  a  typical  day,  in  which,  beginning  at  midnight  with  a  flow 
of  75.32  cubic  feet  per  minute  the  flow  was  reduced  to  70.26  cubic  feet  per  min- 
ute at  6  A.  M.,  130.26  cubic  feet  per  minute  at  11  a.  m.,  123.86  cubic  feet  per 
minute  at  3  p.  m.,  and  steadily  declined  from  this  time  until  midnight,  when 
the  flow  was  75.15  cubic  feet  per  minute.  The  sewer  is  seven  feet,  three  inches 
in  diameter.  It  was  obstructed  by  a  dam,  into  which  was  built  a  twelve  inch 
vitrified  sewer  pipe,  which  was  continued  for  a  length  of  twenty  feet.  The 
gaugings  were  taken  simultaneously  at  three  different  points,  the  average  of 
these  being  the  assumed  depth  through  the  twenty  feet  of  twelve  inch  pipe." 

The  following  is  a  condensed  tabular  statement- of  the 
results  obtained,  as  stated  in  the  report: 


CHAP.  V. 


QUANTITY  OF  SEWAGE. 


81 


TABLE  XI. 

SEWER  GAUGINGS  MADE  AT  ST.    LOUIS. 


DATA. 

DEDUCTIONS. 

D   u 

a 

c 

a 

Velocity  in  Feet 

z 

u. 

per  Second. 

fa2 

~Z 

^S, 

■Ss 

S 

OH 

•-  tLl 

V 

CO  .„ 

■-fc. 

D 

M< 

Do 

Q 

Q  0 

Q 

W> 

.:£&-  . 

a 

<:rTl 

ca 
o 

TO         •  — 

£.SS 

V 

a 
> 

0 

0 

J 

hJ 

< 

< 

0 

J 

< 

March  15-16 

15425 

•5833 

74.67 

-3751 

42.39 

-4356 

5.41 

4-54 

4.69 

19 

144.09 

■5341 

77.64 

-3985 

114.30 

.4689 

5-65 

4-43 

5-27 

"           20 

132.34 

■5144 

67.06 

•  3751 

102.18 

-4519 

5.41 

4.16 

4  94 

"           21 

133-79 

•5177 

68.58 

.3568 

96.49 

.4298 

5-86 

4.27 

493 

"           22 

123.57 

.4961 

69.54 

-3802 

101.78 

-4452 

5-54 

4-23 

5.02 

23 

118.79 

•47OJ 

73-95 

-3725 

79-74 

■3940 

546 

4-47 

4.61 

Typical  I 

)ay,  or  a 

verage 

of  Mar 

Dh 

20,  2 

I  and  22 

100.22 

.4420 

5-86 

4.16 

4-99 

Number  of  houses  connected  with  the  sewer 1.37° 

Population 8,200 

Number  of  water  taps ii39i 

Cubic  feet  of  sewage  discharged  per  capita  in  twenty- 
four  hours 17. 60 

Upon  the  foreg^oing-  statistics,  the  following-  comment  is 

made  in  the  report: 

"A  computation  of  the  amount  of  flow  as  compared  with  the  population 
makes  it  evident  that  the  sewer  must  have  received  a  very  large  amount  of 
ground  water,  for  the  total  flow  (over  1,000,000  gallons  per  day)  amounted  to 
more  than  130  gallons  for  each  member  of  the  population,  which,  in  a  district 
having  only  about  one  water  tap  to  each  house,  would  be  an  impossible  amount. 
It  is  usual  to  estimate  a  maximum  daily  use  for  domestic  purposes  of  about 
thirty-three  gallons  per  head  of  population.  Deciding  the  total  flow  by  this 
amount,  we  might  assume  that  the  twelve  inch  pipe  in  this  instance,  carrying, 
at  its  maximum,  less  than  seven  inches  in  depth  of  water,  was  doing  the  amount 
of  work  that  would  be  required  for  carrying  the  sewage  only  of  a  population  of 
30,000,  -supposing  the  sewers  to  be  absolutely  tight,  so  that  only  household 


82  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

wastes  should  enter  them.  This  last  example  is,  from  its  extent,  and  from  the 
minuteness  with  which  its  details  are  worked  out,  the  most  important  of  the 
series.  It  seems  to  me  to  furnish  a  conclusive  argument — an  argument  fully 
sustained  by  all  of  the  other  gaugings — in  favor  of  the  safety  of  depending  upon 
very  small  conduits  for  the  removal  of  the  dry  weather  flow  of  sewage  of  cities 
and  towns.  It  shows  conclusively  that  the  commission  of  the  National  Board 
of  Health,  which  recommended  the  system  carried  out  in  Memphis— lateral 
sewers  six  inches  in  diameter,  main  outlet  twenty  inches  in  diameter — for  a 
prospective  population  of  60,000,  provided  a  wide  margin  for  contingencies." 

Some  of  the  conclusions  drawn  above  are  not  justified  by- 
recent  experience,  and  do  not  seem  to  be  supported  by  the 
statistics  of  water  consumption  or  by  other  g-aug-ing-s  on 
which  they  are  predicated. 

The  statistics  of  water  consumption  in  St.  Louis  show 
an  averag"e  per  diem  consumption  for  each  tap  of  1,177  gal- 
lons for  the  entire  city.  Assuming  the  territory  tributary 
to  the  sewer  in  which  these  gaugings  were  taken  to  repre- 
sent an  average  consumption  for  the  city,  the  volume  of  sew- 
ag"e  as  found,  17.60  cubic  feet,  or  131.6  gallons  per  diem  per 
capita,  represents  a  trifle  less  than  two-thirds  the  total  aver- 
age water  consumption  for  the  territory  tributary  to  the 
sewer.  The  diversion  of  more  than  one-third  of  the  total 
water  supply  from  the  sewers,  at  the  season  at  which  these 
g'augings  were  made,  would  in  many  cases,  cause  a  public 
nuisance. 

If  the  assumption  of  thirty-three  gallons  per  diem  per 
capita  be  properly  founded  on  the  observations  made,  it 
must  be  from  some  known  local  condition  and  not  solely  on 
the  statistics  as  given,  which  are  not  widely  at  variance  with 
similar  observations  made  at  points  where  it  is  known  there 
can  be  no  infiltration  of  sub-soil  water. 

The  results  of  other  investigations  published  in  the 
report  are  not  reduced  to  gallons  per  diem  per  capita,  but, 
for  the  purpose  of  more  readily  comparing"  them  with  the 
g-augings  made  at  St.  Louis  and  elsewhere,  the  following" 
table  has  been  compiled  from  computations  based  upon  the 


CHAP.  V.  QUANTITY    OF    SKWAGE.  S3 


dimensions  and  measurements  g-iven  in  the  report.  The 
results  were  obtained  by  g"raphical  methods;  but  are  intend- 
ed to  be  closely  approximate. 

The  g-augino-s  were  ordinarily  taken  by  inserting-  a  pipe 
of  smaller  diameter  in  the  sewers,  through  which  the  flow 
was  directed  and  in  which  its  depth  was  measured.  The 
precise  manner  in  which  these  smaller  pipes  were  placed  is 
not  stated  in  every  case,  but,  as  the  object  of  the  gaugings 
was  to  "determine  the  actual  pipe  capacity  required"  in  the 
several  cases,  it  seems  proper  to  assume  that  they  were  so 
placed  as  to  secure  results  identical  with  those  if  the  entire 
sewer  had  been  of  an  equal  diameter.  This  is  assumed  in 
the  computations  made. 

The  gaugings  of  the  College  street  sewer  at  Burlington, 
Vt.,  were  taken  at  intervals  of  fifteen  minutes  from  7:30  a.  m. 
to  10:30  A.  M.  The  district  which  it  drains  contains  eighty- 
five  houses,  of  which  fifty-four  are  connected  with  the  sewer. 
The  population  tributary  to  the  sewer  embraces  325.  There 
were  two  equal  maxima  in  the  flow,  one  occurring  at  7:45 
A.  M.,  and  the  other  at  "J  a.  m.  The  mean  rate  of  discharge  in 
this  case  does  not  represent  the  mean  daily  rate,  but  the 
mean  rate  during  the  time  the  gaugings  were  taken — 7:45 
A.  M.  to  9  A.  M. 


84 


THE    SEPARATE   SYSTEM    OF    SEWERAGE. 


O 

o 

< 
o 

X     g 

3  ^ 

«    fe 
<:   o 

o 

S 

<; 


;39j  ui  q^Sagq 


&    ni 

0)   rt  nil 

>  'n  a 

<  a  rt 


a  3 

si 


2  o- 

-    -  ac  c 

D    (U    OJ    O    IK 

S  6:^  b  E 

CA)  cn  U  K  C/3 


rt 

■lUnLUIXBJ\[ 

N   moo   O   O   ^                   O        lO 
or^t^'rNa\                co        r^ 

N      M      tH      M      t-l                                                                      M 

Q  ^ 

•aE9i^ 

M      Tf    M      U-) 

N    m  ro  M 

M      M      W      M 

a. 

niniuiuij^ 

00   o   Tl-  m 

On  0^  CJivO 

m 

ro 

<    • 
D  o 

0, 

U9M9S  O} 

XaBjnqux 

in  t^ 
M   t^ 

m  M 

IBIOX 

8,200 
8,20O 
8,200 

in                   o        O 

m                   O         O 
O                    o         o 
-f                  in       M~ 

o 

X 

•mnuiixHj\[ 

o  r-  m  o  o  o                 3~, 
o  H  M  N  m  m 

■nB9i^ 

N  N  o  T^ 
M   -^  m  o 
m  >n  m  M 

h  Z 

u 

Q 

•uinuiinii\[ 

O    O    Tf  O 
m  in  'j-oo 
•f  -^  Tt- 

O 
in 

CO 

OOI   J9d  llEjJ 

■  •     ■  M   in  in                   lO        O 

■  ■      ■    M    N    N                        VO          lO 

M 
.     M 

■s9qoni 
ai  j949mBiQ 

PJNNOOO                           O          O 

M      M      M                MM                                       N 

D 
C 

a; 

a 
a) 

tn 

J3 

J3 

^ 

a 

a 

o 

?^ 

01 

M-H 

^ 

o 

"o) 

b 

o 

N 

-_^ 

>. 

H 

3 

o 

< 

CI 

0) 

W 

n! 

rt 

§ 

en 

CHAP.   V.  QUANTITY    OF    SEWAGE.  85 

The  following-  is  an  account  of  the  g"aug-ing-s  taken  in  the 
Memphis  main  sewer  by  C,  H.  Latrobe,  C.  E,,  and  is  quoted 
from  his  report  to  the  Mayor  and  City  Council  of  Baltimore: 

"By  gaugings  taken  at  the  head  of  the  twenty-inch  main  I  found  the 
hourly  flow  of  sewage  to  be  remarkably  uniform.  Thus,  from  six  a.  m.  till  one 
A.  M.  the  following  morning,  a  period  of  twenty  hours,  the  flow  oscillated  in 
centre  depth  from  twelve  and  one-half  to  fourteen  and  one-half  inches,  the 
minimum  area  of  flow  being  206.5  square  inches;  the  maximum  245.73  square 
inches.  From  one  a.  m.  till  5  a.  m.,  a  period  of  four  hours,  the  centre  depth  of 
flow  varied  from  eight  and  one-half  inches  to  eleven  and  one-half  inches,  mini- 
mum area  being  107.6  square  inches;  maximum  area,  186.9  square  inches. 
Taking  the  twenty-four  hours,  the  minimum  flow  is  43.7  per  cent,  of  the  max- 
imum; taking  the  twenty-four  hours  of  greatest  flow,  the  minimum  is  84  per 
cent,  of  the  maximum  and  eight-ninths  of  the  daily  flow  of  sewage  passed  in 
twenty  hours,  one-ninth  in  four  hours.  This  marked  uniformity  of  flow  during 
twenty  hours  of  the  day,  and  its  oscillating  character  within  such  limits,  must 
be  somewhat  influenced  by  the  action  of  the  flush-tanks,  which  probably  dis- 
charge in  small  groups.  *  *  *  The  accompanying  system  of  tile  drains  has 
also  thoroughly  drained  (as  far  as  I  know)  the  very  tenacious  sub-soil  of  the 

Cltv         4f       "fr       w       w       ^ 

"The  errors  or  omissions  in  the  Memphis  system  are: 

"First.  Insufficient  size  in  the  mains  to  accommodate  the  excessive  use  or 
waste  of  water  during  severe  winters,  when  people  allow  spigots  to  run  all  the 
time,  to  prevent  freezing.  During  the  winter  just  ended  Major  Humphries 
estimates  that  one  hundred  gallons  per  capita  per  day  were  often  used,  which 
caused  the  mains  to  run  filU  bore  and  occasioned  a  backing  lip  of  the  sewage  in 
the  lower  parts  of  the  city.  This  fault,  of  course,  was  not  incident  at  all  to  the 
system,  but  was  an  oviersight  in  proportioning  the  mains,  and  would  not  be  felt 
during  an  ordinary  winter." 

Since  in  the  case  of  Memphis  special  provision  was  made 
for  the  removal  of  the  sub-soil  water  by  separate  channels,  it 
is  improbable  that  the  flow  of  the  sewers  proper  was  aug:- 
mented  by  it. 

It  must  be  borne  in  mind  that  these  g^augfinofs  were  made 
before  the  completion  of  the  system  at  Memphis,  and  repre- 
sent the  discharg-e  from  but  a  limited  portion  of  the  territory 
upon  which  the  per  capita  dischargfe  is  based,  there  being  at 
that  time  but  twenty  miles  of  the  system  complete.  It  has 
since   been   extended   to  about   fortv  miles.      On  the  other 


86  THE    SEPARATE   SYSTEM    OF    SEWERAGE. 

hand,  the  introduction  of  the  system  into  the  houses  was  so 
g-eneral  and  prompt,  that  it  is  probable  the  territory  sewered 
reached  more  nearly  its  maximum  rate  of  discharg-e  within 
the  short  time  intervening-  between  its  completion  and  the 
time  at  which  the  g-aug-ing-s  were  taken  than  would  ordinarily 
be  the  case. 

The  maximum  rate  of  sewage  discharg^e,  then,  as  shown 
in  Table  XII  (eig"hty  g-allons  per  diem  per  capita),  should 
properly  be  based  on  a  much  smaller  population  than  35,000. 
(The  total  population  of  the  city,  as  g-iv^en  in  the  census  of 
1880,  is  but  33,590.)  No  means  of  determining-  the  popula- 
tion occupying-  the  territory  actually  tributary  to  this  twenty 
miles  of  sewers  are  at  hand,  but  it  has  been  estimated  at 
20,000.  Upon  this  basis  the  maximum  rate  of  discharg-e  of 
eig-hty  gallons,  as  shown  in  the  table,  becomes  140  g-allons. 

The  population  actually  tributary  to  the  Compton 
Avenue  sewer  at  St.  Louis  is  not  stated.  If,  in  the  case,  of 
theg-augings  made  in  this  sewer  on  Saturday,  March  20,  it  be 
assumed  that  at  the  time  of  minimum  flow,  the  entire  volume 
discharg-ed  was  sub-soil  water  (which  is  certainly  not  a 
proper  assumption,  since  at  no  time  during-  the  twenty-four 
hours  is  the  discharg-e  of  house  sewage  in  a  system  of  any 
extent  wholly  arrested),  and  its  total  amount  at  this  assumed 
rate  for  the  twenty-four  hours  be  deducted  from  the  dis- 
charg-e as  shown  by  the  g-aug-ing-s,  the  volume  of  discharg-e 
remaining-  agg-reg-ates  1:3.4  g-allons  per  diem  per  capita. 

Again,  if  we  assume  the  hourly  variations  of  flow,  as 
determined  by  the  g-aug-ing-s  taken  at  Memphis,  to  be  a 
proper  rang-e  for  St.  Louis,  or,  in  other  words,  assume  that 
the  ratio  of  minimum  and  maximum  discharg-e  of  house  sezv- 
apx  only,  in  the  two  cities  is  the  same,  we  can  determine  the 
amount  of  sub-soil  water  and  eliminate  it.  A  computation 
made  on  this  assumption  g-ives  us  in  St.  Louis,  for  the  dis- 
charg-e of  house  sewag-e  only,  when  based  on  the  total  popu- 


«5 
05 

CO 

10 

IN 

C 
CM 

U5 

C 

0 

c 
0 

0 

c» 

■r^       "O       0       "3       Oi      «i 

0;         00[       oc'        1^         l^         CO 

!      '      ' 
1       !   „..i^. 

0 

^ 

■^ 

1 

— 0' 

^ 

•nr^ 

>i-IOI 

§ 

>' 

i 

< 

/ 

Q 

0 

'a 
h 

/ 

Z''V 

7i77.l    \ 

/ 

•osi- 

^ 

' 

. 

^^ 

~^ 

--^ 

., \ 

1 

~~~ ~~--— —i^ 

:     !'°"l.\ 

r 

i 

;    J  „" 

fi;:piL/ 

' 7.P 

0.1 — 

/ 

3 
c 

u 
> 

<: 

B 
O 

a. 

& 
o 
O 


•ifi! 

86l 

1.       1^^ 

CD-li 

^ 

0 
OJ 

0 

t 

09-16 

' 

/ 

i 

^•-io 

1    1 

^^ 

".  '"7 

^tE-?.e.-L 

1 

1 

1        1 

i 
i 

! 

''f*"'"^ 

\ 

1 

=  1 

1 
1 

cs 

U 
3 

-Hi 

OS 
0) 

i 
< 

1  . 

\ 

)ft5oT 

^^^HT 

_ 

51 

) 

mz-V 

-J' 

— '''■a 

^-A 

' 

bo 
C 
'Sj 
3 
M 
O 


CHAP. 


QUANTITY    OF    SKWAGE. 


89 


lation  occupying-  the  territory,  minimum,  65  g-allons;   mean, 
102  g-allons;  maximum,  IttH  g-allons  per  diem  per  capita. 

The  g-aug-ing-s  made  at  the  Compton  Avenue  sewer,  St. 
Louis,  cover  the  entire  twenty-four  hours.  They  are  illus- 
trated g-raphically  in  the  diag-rams  on  pag-e  87,  taken 
from  the  report. 

Gaug-ing-s  were  made  of  the  flow  of  the  Water  Street 
Main  in  Kalamazoo,  Mich.,  on  March  9,  1885,  as  follows: 


TABLE   XIII. 

DISCHARGE    OF    WATER    STREET    MAIN    SEWER,     KALAMAZOO,     MICHIGAN, 
MONDAY,     MARCH    9,     1S85. 


Time. 


Q° 


233 
227 
224 
230 

234 
242 
244 
265 

255 
265 
258 

258 

255 
265 

273 
287 

275 
276 
265 
257 
255 
255 
253 
250 


Minimum 


Maximum 


Average  discharge  per  min- 
ute    254  Gallons. 

Maximum      discharge      per 

minute 287  Gallons. 

Minimum      discharge       per 

minute 224  Gallons. 


Percentage  Relation  of  Maximum  and 

Minimum  Discharge  to  Mean 

Discharge. 


Minimum  discharge 88 

Mean  discharge 100 

Maximum  discharge 113 


90 


THE   SKPAKATE    SYSTEM    OF    SEWERAGE. 


These  g-aug^ing-s  at  Kalamazoo  were  made  by  weir  meas- 
urement in  the  manner  illustrated  in  Fig-.  1. 

The  weir  is  made  of  galvanized  sheet  iron  of  the  ordi- 
nary weig-ht,  rolled  up  in  the  form  of  a  funnel,  and  riveted  or 
lapped  and  soldered,   its  smaller  end  being-  slightly  smaller 


^ly 


Fig.    1. 
in  diameter  than  the  sewer  in  which   it  is   to   be   inserted. 
The  larger  end  is  cut  off  at  rig-ht  angles  to  the  side  which  is^ 
to  lie  in  the  bottom  of  the  man-hole,  and  on  this  is  fastened 
an  end,  having-  cut  in  it  the  notch  forming-  the  weir,  as  shown 


CHAP.  V.  QUANTITY    OI'^    SKWAG]-:.  91 

at  h.  The  weir  should  stand  sufficiently  above  the  man-hole 
to  counteract  the  effect  of  velocity  of  entry,  and  to  g"ive  a 
free  run  to  the  sewag"e.  The  depth  of  discharg^e  over  the  weir 
is  measured  by  a  thin,  g-raduated  strip,  on  which  travels 
a  block  having-  a  level  attached  for  bring-ing  the  scale  into 
a  vertical  position,  and  the  point  of  contact  with  the  surface 
of  the  water  level  with  the  index  or  point  of  reading  at  d. 
Still  more  accurate  results  might  be  had  by  taking  the  meas- 
urement from  some  fixed  point  above  the  weir,  but  in  ordi- 
nary cases  the  method  detailed  above  will  be  sufficiently 
accurate. 

The  weir  is  easily  transferred  from  one  point  to  another, 
and  is  quickly  set,  requiring  but  a  piece  of  cloth  wrapped 
around  the  lower  part,  when  it  can  be  crowded  into  the  lower 
branch  of  a  man-hole,  where  its  flexibility  insures  a  perfect 
fit,  and  the  pressure  of  water  from  above  keeps  it  to  its 
place.  It  is  also  very  convenient  in  use,  the  observation 
being  taken  from  above,  where  the  peculiar  light  makes  the 
least  ripple  of  water  against  the  point  r,  and  the  position  of 
the  level  bubble  plainly  disting-uishable. 

The  method  of  observing-  the  depth  of  flow  in  the  sewer 
proper  and  computing  from  these  data  the  discharge  by  for- 
mula or  tables,  though  frequently  used,  is  liable  to  error. 
The  slightest  obstruction  below  the  point  of  observation 
increases  the  observed  depth,  and,  consequently,  g-ives 
results  too  hig-h,  since  the  diminished  velocity  at  the  point  of 
observation  is  not  noted.  A  slight  increase  of  flatness  in  the 
grade  at  the  point  at  which  the  observ^ations  are  taken,  below 
the  grade  at  which  the  sewer  may  have  been  laid  orig-inally, 
has  the  same  efi^ect,  as  also  the  depression  of  a  sing-le  joint  or 
section  of  pipe.  Opposite  conditions,  by  increasing-  the 
velocity  or  by  raising  the  measuring-  scale,  w^ll  g-ive  results 
too  low. 

In  the  case  of  pipes  of  smaller  diameter  inserted  in 
larger  sewers,  there  are  also  difficulties  in  the  way  of  secur- 


92  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

ing-  correct  results.  The  following-  g-aug-ing-s,  made  at  Mil- 
waukee, will  illustrate  this  point.  They  were  made  under 
the  direction  of  G.  E.  Waring-,  by  A.  H.  Scott,  C.  E.,  for  the 
National  Board  of  Health,  and  a  statement  of  them  appears 
in  the  report  of  1880.  They  were  made  in  this  way  for  a 
particular  object: 

"Formulae  in  use  among  engineers  would  lead  us  to  substantially  the  same 
result  with  actual  gaugings,  but  their  educational  effect  would  be  less  marked, 
because  calculations  based  upon  scientific  formulae  are  less  readily  compre- 
hended by  the  a\erage  municipal  ruler.     *     *     * 

"The  grade  of  the  sewer  at  the  point  where  the  gaugings  were  taken  is 
about  I  in  400.  The  greatest  flow  in  the  main  sewer  on  'washing  day' — the 
greatest  flow  of  the  week — attained  a  depth  of  six  inches,  the  diameter  of  the 
sewer  being  forty-two  inches.  The  channel  being  reduced  to  a  diameter  of  ten 
inches,  the  greatest  depth  of  flow  was  4.5  inches.  Reduced  to  a  diameter  of 
eight  inches,  the  depth  remained  the  same — 4.5.  Reduced  to  a  diameter  of  six 
inches,  it  reached  a  depth  of  55  inches.  The  influence  on  the  velocity  of  the 
stream  by  increasing  its  hydraulic  mean  depth  is  illustrated  by  the  following 
figures: 

"Forty-two  inch   sewer,    six  inches    deep; 

cross  section  of  stream 121  3    square    inches. 

Ten    inch    sewer,    4.5    inches  deep;    cross 

section  of  stream 33.1     square    inches. 

Eight    inch    sewer,   4.5  inches  deep;  cross 

section  of  stream 27  7    square    inches. 

Six    inch    sewer,    5.5    inches    deep;     cross 

section  of  stream 27. 14    square    inches." 

These  lig-ures  illustrate  very  forcibly  the  superior 
cleansing-  effect  of  sewers  discharg-ing-  half  full  or  more. 
They  also  illustrate  the  difficulty  in  securing-  uniform 
results  previously  cited,  as  shown  b}"  the  following-  computa- 
tions. The  volume  discharg-ed  in  each  case  is  stated  as  the 
same.  The  computed  discharg-e  is,  approximately,  as  fol- 
lows, leaving-  out  of  consideration  the  fortv-two  inch  sewer: 


CHAP.  V. 


QUANTITY    OF    SEWAGE. 


93 


Diameter. 

Depth. 

Discharg-e  in  Cubic  Ft. 

10  inches. 
8  inches. 
6  inches. 

4.5  inches. 
4.5  inches. 
5.5  inches. 

30.45 
23.06 
17.48 

The  inaccuracies  of  this  manner  of  measuring"  flow 
become  still  more  apparent  as  the  depth  of  flow  becomes  less 
in  proportion  to  the  diameter  of  sewer. 

From  the  statistics  of  water  consumption  in  the  preced- 
ing- pages,  we  mav  conclude  that  the  discharge  of  house 
sezvage,  at  its  maximum  hourly  flow  during  the  year,  is 
approximately  twice  the  mean  discharg-e. 

The  records  of  sewage  discharge  show^  a  variation  dur- 
ing single  days  covered  by  the  observations  of  thirty,  forty, 
and  in  the  case  of  the  Compton  Avenue  sewer  at  St.  Louis, 
on  March  15  and  16,  of  nearly  seventy  per  cent,  above  the 
mean  daily  rate.  Observations  covering-  a  long-er  period  and 
varying  conditions  of  temperature  would,  undoubtedly,  indi- 
cate a  still  greater  maximum  rate  of  discharge. 

Subsoil  Water. — The  probable  amount  of  subsoil  water 
sometimes  requires  consideration  in  proportioning-  the  sizes 
of  sewers.  This  is  a  most  difficult  factor  to  determine. 
Although  an  effort  should  be  made  to  lay  the  pipes  with 
water  tight  joints,  the  trenching  is  sometim'es  so  difficult 
that  it  seems  well  nigh  impossible  to  do  so  and  instances  are 
on  record  where  the  ground  water  found  its  way  into  the 
pipes  throug-h  imperfect  joints  to  such  a  degree  as  to  occupy 
nearly  the  capacity  of  the  sewers  before  any  sewag^e  had 
been  admitted  to  them. 

In  some  instances  it  is  desirable  to  discharg-e  subsoil 
drains,  laid  parallel  with  the  sewers,  into  the  sewers  proper 
at  a  lower  level  and  when  this  is  done  a  judicious  allowance 
for  subsoil  water  is  particularl}-  important. 


94  THK    SEPARATK    gYSTEM    OF    SEWERAGE, 


CHAPTER  VI. 

LAWS  OF  FLOW  IN  SEWERS. 

A  circular  sewer  reaches  its  g^reatest  capacity  of  dis- 
charg"e  when  its  depth  of  flow  is  about  .933  of  its  diameter, 
being"  at  this  point  nearly  eleven  per  cent,  in  excess  of  that 
attained  when  running-  full.  When  the  depth  of  flow  is  half 
the  diameter,  the  velocity  is  equal  to  that  when  the  sewer  is 
running  full  and  not  under  pressure. 

Circular  sewers  should  be  so  proportioned  as  to  size, 
throughout  the  system,  that  the  depth  of  the  ordinai'y  daily 
flow  will  be  sufficient  to  induce  a  fair  velocity,  and  prevent 
deposits. 

The  transporting  power  of  circular  sewers  of  small 
diameter  is  dependent  on  the  depth  of  flow  in  a  g^reat  meas- 
ure, as  well  as  on  grade  and  velocity.  A  stream  having-  a 
depth  of  flow  sufiicient  to  immerse  solid  matter  held  in  sus- 
pension, to  a  certain  extent  lifts  it  and  carries  it  forward. 
The  entire  surface  is  also  exposed  to  the  action  of  the  cur- 
rent. A  stream  having  an  equal  velocit}'  but  a  less  depth  in 
proportion  to  the  diameter  of  the  solid  matters  to  be  trans- 
ported, evidently  has  less  transporting  power.  As  an  illus- 
tration, a  stream  can  be  easily  forded  when  its  depth  is 
below  a  man's  waist,  while  the  same  stream  in  deeper  water, 
even  though  the  velocity  be  less,  will  carry  a  person  down 
stream. 

Effect  of  Increasing  Size.^ — An  amount  of  sewag-e  which 
can  be  properly  transported  by  a  circular  sewer  of  a  given 


CHAP.  VI. 


LAWS    OF    FLOW    IN    SEWERS. 


95 


size,  cannot  be  as  efficiently  transported  by  one  of  larger 
diameter,  as  the  following-  comparison  will  show:  If  we 
assume  the  contents  of  a  sewer  of  six  incbes  in  diameter,  laid 
at  a  grade  of  .5  per  hundred,  and  discharg-ing-  half  full,  to  be 
diverted  to  sewers  of  eig^ht,  ten,  twelve  and  fifteen  inches  in 
diameter  respectively,  and  laid  at  the  same  g^rade,  the  follow- 
ing depth  and  velocities  will  be  attained  theoretically: 

TABLE  XIV. 

ILLUSTRATING    EFFECT    OF    INCREASED    SECTION,    THE    VOLUME    OF    DISCHARGE 
REMAINING    THE    SAME. 


SEWER. 

Depth  of  Flow. 

Velocity  in  Feet 
per  Minute. 

Discharge  in 

Cubic  Feet  per 

Minute. 

6  inch  sewer. 
8     " 

lO       " 

12 

15     " 

3.00  inches. 
1.92 

1.36        •• 
1.03 

•75 

147 
129 

1X2 
ICO 

83 

14.40 
14  40 
14.40 
14.40 
14.40 

From  tbe  above  comparison  we  see  that,  treated  purely 
as  a  problem  in  hydraulics,  both  the  velocity  and  depth,  each 
of  which  is  a  factor  in  the  transporting-  power  of  the  sewer, 
and,  consequenth'  in  a  deg-ree,  a  measure  of  its  effectiveness, 
decrease  as  the  size  of  pipe  is  increased.  Like  results  have 
been  shown  practically  in  man}^  cases,  by  the  substitution  of 
lateral  sewers  of  smaller  diameter  in  place  of  those  which 
have  not  had  depth  of  flow  sufficient  to  be  self-cleansing-. 

It  should  be  borne  in  mind,  however,  that  while  the 
above  reasoning-  is  entirely  pertinent  as  applied  to  the  treat- 
ment of  a  liquid  that  sewers  are  liable  to  be  the  receptacles 
of  a  certain  amount  of  solid  and  refuse  matter  which  some- 
what modifies  the  above  conclusions  in  some  instances. 

The  most  perfect  working-  of  the  house  sewers  demands 
that  they  have  a  free  out-fall  into  the  lateral,  as  shown  by  the 
section  in  Plate  I.      A  majority  of  the  stoppag-es  in  house 


96  THE   SKPARATE    SYSTEM    OF    SEWERAGE. 

sewers  occur  at  their  entrance  into  the  laterals  and  mains, 
and  if  the  flow  in  the  laterals  and  mains  be  deep  enoug^h  to 
seal  the  outlet  of  the  house  sewers,  the  discharg-e  of  floating- 
paper,  etc.,  is  arrested,  and  the  difficulty  at  this  point  very 
much  ag-g-ravated.  Good  ventilation  also  demands  a  free 
passagfe  of  air  currents  throug^h  every  part  of  the  mains, 
laterals  and  house  drains.  The  connection  of  the  house 
sewer  with  the  street  sewer  is  ordinarily  and  properly  made 
with  the  common  Y  branch,  elevated,  as  shown  by  section  in 
Plate  I.  It  is  not  made  right  and  left  hand,  and  when  laid 
the  sewer  cannot  be  charg-ed  more  than  half  bore  without 
setting-  up  into  the  house  drain.  The  ordinary  daily  flow, 
then,  for  the  reasons  stated,  and  for  other  pertinent  reasons 
that  will  appear  later,  should  be  accommodated  below  the 
horizontal  diameter.  An  occasional  extreme  discharg-e  of 
short  duration,  reaching-  the  full  capacity  of  the  sewer,  will  be 
beneficial  rather  than  otherwise. 


PLATE  I. 


\IJl:I,iI,iI,i,I,iI,iI,,MjjaljIuj 


SELF     READING     ROD 


LOCATION   OF   Y'S 
ON    LINE   A  B 


S;^3Ki''--^ 


^■-i-;;  fi 

"nflT'vV 

^ 

t^' 

„.>v„ 

r'^'.'  ■ 

,-»s>. 

h'^  ■ 

, 

ll,\"^' 

V^r 

U  ■'^^" ' 

'-.  Ill 

'1 

•fZ'.   ; 

^r=?'.;l 

I'^T 

xS; 

1 

■  ".V 

^s'-^ 

ips- 

1 

'^'    ■ 

-.'■Vf;.!  • 

■■'#. 

•■•(^i: 

!"l 

■:f(l1-- 

*  '^'r  ' 

^ 

■'  -%: 

f^T*". 

;J  .--l- 

ri: 

■V/-'.'. 

TEMPORARY    OSSERVA  riON' 
DEAD  END  OPENING 


LAWS    OF    I'^LOW    IN   SICWICKS. 


y!> 


Effect  of  Hydraulic  Mean  Radius.— The  comparative 
velocity  and  discharg-e  of  circular  sewers  when  running-  at 
different  depths,  is  well  illustrated  by  the  following-  table: 

TABLE  XV. 

SHOWING    THE    COMPARATIVE    DISCHARGE    AND    VELOCITY    IN    CIRCULAR    SEWERS 
OF    A    GIVEN    DIAMETER    AND    GRADE    FOR    VARIOUS    DEPTHS    OF    FLOW. 

[The  depth  of  flow  is  expressed  in  terms  of  the  diameter.  The  velocity 
and  discharge  are  expressed  in  terms  of  the  velocity  and  discharge  when  the 
sewer  is  running  full,  or  when  depth==i.] 


Depth  of  Flow. 

Velocity.              Disc 

.harge. 

.067 

.414 

0119 

.100 

.498 

0260 

■1465 

602 

0548 

.200 

.6942 

0989 

.250 

.7698 

1497 

.300 

.8210 

2072 

400 

.9264 

3457 

.500 

I.OOOO 

5000 

.600 

10534 

6598 

700 

1.0932 

8174 

.750 

I  0984 

8836 

.800 

I. 1028 

9458 

•«535 

I.IOIO                       I 

0009 

.900 

I  0918                I 

0351 

933 

1.0794            I 

0479 

1. 000 

I  0000                I 

0000 

If  from  the  above  table  we  construct  the  curves  of  velo- 
city and  discharg-e  by  laying-  off  the  depth  of  flow  and  the 
velocity  and  discharge  as  co-ordinates,  the  effect  of  the 
respective  depths  of  flow  upon  velocity  and  discharg-e  will  be 
more  apparent  to  the  eye. 


Q 

c 

> 

'So 


o 
O 

bo 
c 

'% 
o 

Xi 

tn 


>    a 


CHAP.   VI.  LAWS    OF    FLOW    IN    SEWKKS.  101 

Computation  of  Discharge  and  Velocity  for  any  Diameter 
and  any  Depth  of  Flow. — The  diagram  affords  a  very  con- 
venient and  closely  approximate  method  of  computing-  the 
discharg-e  of  any  circular  sewer  discharg-ing-  at  anv  depth. 

Nearly  all  hydraulic  tables  bearing-  on  this  subject  are 
computed  to  give  the  discharg-e  of  sewers  running-  full  bore. 
A  few  give  the  discharg-e  when  flowing  one-quarter,  one- 
third,  one-half,  two-thirds  or  three-quarters  full.  This  is 
about  as  wide  a  rang-e  as  can  be  covered  without  making-  the 
tables  too  bulky  for  convenience. 

The  discharg-e  of  a  circular  sewer  of  any  size  and  g-rade, 
and  flowing-  at  any  depth,  can  be  determined  from  the  dia- 
gram, as  follows: 

Divide  the  depth  of  flow  by  the  diameter,  and  from  the 
fractional  depth  on  the  vertical  diameter  thus  indicated  draw 
(by  the  eye)  a  horizontal  line,  intersecting-  the  curve  of  dis- 
charg-e, and  from  its  point  of  intersection  a  vertical  to  the 
base.  The  percentag-e  thus  determined  on  the  base,  will  be 
the  relation  of  the  discharg-e  required  to  the  discharg-e  of  the 
sewer  when  running-  full,  which  can  be  taken  from  the  table 
thus: 

Given, 

Diameter  of  sewer  =  12  inches. 
Grade  =1  in  200. 

Depth  of  flow  =5  inches. 

Required  the  discharge. 

Solution: 

5 

—  =  .416. 
12 
Tracing  a  horizontal  line  from  .416  on  the  vertical  diam- 
eter to  its  intersection  with. the  curve  of  discharge,  we  read 
from  the  scale  below  .36.  The  discharge  is  thirt3'-six  per 
cent,  of  that  if  the  sewer  were  running  full.  From  Baldwin 
Latham's  Tables  we  see  discharge  when  running-  full  =  167.2 


102  THE    SEPARATK    SYSTEM    OF    SEWERAGE. 

cubic  feet  per  minute.  167.2  X  .36  =  60.192  cubic  feet  per 
minute,  which  is  the  required  discharg-e. 

The  velocity  of  any  circular  sewer,  flowing-  at  any  depth, 
can  be  ascertained  from  the  diag^ram  in  the  same  way.  The 
diag-ram  has  been  carefully  reduced  to  scale  of  one-half  inch 
horizontal  and  one-fourth  inch  vertical,  to  facilitate  calcula- 
tions of  this  kind,  and  the  fractional  divisions  can  be  read  by 
applying-  an  ordinary  eng"ineer's  scale. 

It  is  probable  that  neither  the  velocity  nor  discharg-e  of 
sewers,  whose  depth  of  flow  is  but  a  small  percentag-e  of 
their  diameters,  attain  in  practice  the  value  theory  ascribes 
to  them,  since  the  solid  matter  held  in  suspension  in  all  sew- 
ag-e  becomes  partiall}^  stranded,  or  is  not  lifted  clear  of  the 
invert  of  the  sewer,  and  th^  co-efficients  of  resistance 
appearing-  in  the  formula,  being-  applicable  to  a  liquid  only, 
g-ive  results  too  g-reat. 

Velocity  Required  to  Prevent  Deposit. — The  velocity 
necessary  to  prevent  deposit  in  sewers  is  variously  esti- 
mated at  from  one  to  three  feet  per  second  by  difi:erent 
authorities.  Baldwin  Latham  states  that  he  has  found  that, 
in  order  to  prevent  deposits  in  small,  circular  sewers,  such 
as  those  of  six-inch  and  nine-inch  diameter,  a  velocity  of  not 
less  than  three  feet  per  second  should  be  produced.  Sewers 
from  twelve  to  twenty-four  inches  in  diameter  should  have  a 
velocity  not  less  than  2J4  feet  per  second,  and  sewers  of 
larg-er  diameter  should  in  no  case  have  a  less  velocity  than 
two  feet  per  second.  The  minimum  inclination  securing- 
these  velocities  in  the  several  cases,  assuming;  the  sewers  to 
run  half  full,  or  full,  is: 

6-inch  pipe 1  in  142  =  ,701  per  100 

9-inch  pipe 1  in  203  =  .494  per  100 

12-inch  pipe 1  in  385  =  . 260  per  100 

24-inch   pipe 1  in  775  =  . 129  per  100 


CHAP.  VI.  LAWS    OI'^    FLOW    IN    SIC  WICKS.  103 

The  minimum  velocity  recommended  by  several  author- 
ities is  as  follows: 

Baldwin   Latham  .  .  .2      to  3  feet  per  second. 

Beardmore 2)4  to  3  feet  per  second. 

J.   Phillips 2^^'2  to  3  feet  per  second. 

Rankin 1      to  4  feet  per  second. 

J.  W.  Adams 2^4  to  3  feet  per  second. 

Philbrick 2^2  to  3  feet  per  second. 

Gerhard 2      to  3  feet  per  second. 

While  in  extreme  cases  sewers  may  be  laid  at  an  inclina- 
tion inducing^  only  a  velocity  of  two  feet  per  second,  with 
reasonable  expectation  of  their  serving-  a  g^ood  purpose,  it 
cannot  be  denied  that  they  are  less  satisfactory  in  their 
working's,  and  require  more  care  in  their  maintenance, 
especially  in  the  upper  levels  of  the  system,  where  the  vol- 
ume of  sewag^e  is  less  constant. 

Effect  of  Decreasing  Quantity  of  Sewage. — It  must  be 
borne  in  mind  that  the  flow  decreases  in  volume  in  arithmet- 
ical ratio  as  we  ascend  the  sewer,  becoming-  zero  at  the  sum- 
mit. In  illustration:  If  we  assume  a  six-inch  sewer  4,000 
feet  long',  with  a  g-rade  of  AH  per  100,  to  have  a  tributar}'  pop- 
ulation for  each  100  feet  of  its  leng-th  of  fifty  persons,  and 
each  person  to  contribute  fifty  g'allons  per  day  of  sewag^e,  to 
be  discharg-ed  in  sixteen  hours,  with  the  sewer  running-  half 
full,  the  computed  maximum  velocity  at  its  lowest  level, 
becomes  approximately,  144-  feet  per  minute.  The  volume 
of  sewag-e,  however,  at  distances  of  250,  500,  1,000,  2,000  and 
3,000  feet  from  its  summit,  is  but  Vie,  's,  X,  /i  and  H  of  that 
at  the  point  where  it  is  running-  half  full,  and,  by  computa- 
tion, supposing-  the  sewer  laid  at  a  uniform  grade,  the  theo- 
retical velocities  at  these  points  become,  approximately,  as 
follows: 


104 


THE    SEPARATE    SYSTEM    OF    SEWERAGE. 


Distance 


.   250  ft.     Velocity 

.   500  " 

.1000  " 

.2000  " 

.3000  " 

.4000  " 


73.4    ft.  per  min. 

89. 
105.11 
124.42 
135.88 
144. 


Or,  assuming"  the  inclination  to  be  increased  as  we 
approach  the  summit,  so  that  the  velocity  shall  be  main- 
tained at  the  uniform  rate  of  144  feet  per  minute,  the  inclina- 
tion at  the  several  points,  theoretically,  becomes  about  as 
follows: 


DISTANCE. 

INCLINATION. 

250  feet 

1  in    58.8=  1.700  per  100 

500     "    

1  "    85.   =  1.176    "    100 

1000     "   

1  "  113.3=     .870    "    100 

2000     "   

. 1  "  158.   =     .632    "    100 

3000     "   

1  "  185.   =     .540    "    100 

4000     "   

1  "  208.    =     .480    "    100 

These  fig"ures  very  plainly  illustrate  what  is  so  often 
observed  in  practice,  and  explain  the  frequency  of  stoppagfes 
in  the  hig"her  levels  of  a  system  of  sewers.  They  also  illus- 
trate the  g"reat  benefit  to  be  derived  from  the  use  of  auto- 
matic flushing-  tanks  at  dead  ends,  by  which  the  sewer  is 
intermittently  filled  to  a  fair  working-  capacity,  and  its 
stranded  contents  swept  on  to  the  mains  before  they  have 
accumulated  to  a  deg-ree  interfering-  with  the  working-  of  the 
sewer.  Flushing-  tanks  at  dead  ends  so  surely  counteract 
the  defects  above  stated,  that  lateral  sewers,  to  which  they 
are  applied  may  be  desig-ned  with  uniform  inclination 
throug-hout. 

The  grade  of  streets  frequently  prevents  the  inclination 
of  sewers  being  increased  to  the  proper  deg-ree  toward  the 
summits,  and  in  this  case  flushing-  is  indispensible. 


CHAP.  VI. 


LAWS    OI'    FLOW    IN   SEWP:RS. 


105 


Minimum  Velocity. — Six-inch  lateral  sewers  laid  at  a 
grade  of  A  per  100  (1  in  250)  are  fairly  satisfactor}'  in  their 
working's,  when  supplied  with  automatic  flushing-  tanks. 
The  theoretical  velocity  in  this  case  is  VM  feet  per  minute 
when  running-  half  full.  There  is  a  marked  difference 
observed,  however,  when  the  inclination  is  increased  to  .5 
per  100,  and  the  velocity  to  147  feet  per  minute,  especially 
during-  that  portion  of  the  day  when  the  sewer  is  discharg-ing- 
below  its  averag-e  rate.  Sewers  of  this  diameter  and  g-rade 
are  uniformly  found  in  g-ood  condition  when  properly  con- 
structed and  maintained;  and,  unless  there  is  g-ood  reason  to 
the  contrary,  the  inclination  should  be  sufficient  to  secure 
this  velocity.  The  velocity  in  sewers  of  larg-er  diameter 
may  be  somewhat  less,  as  being-  ordinarily  mains,  their  flow 
is  more  constant,  and,  having-  a  g-reater  actual  depth  of  flow, 
suspended  matters  are  wholly  immersed  and  lose  weight  in 
a  greater  degree,  and,  consequently,  are  transported  at  a 
lower  velocit}'. 

Unless  special  means  are  taken  to  prevent  deposit,  the 

following  may  be  taken  as  minimum   velocities   in   circular 

pipe  sewers: 

TABLE  XVI. 

MINIMUM    VELOCITIES    AND    GRADES    IN    CIRCULAR    SEWERS 


Theoretical  Inclination  when  depth  of 

Velocity  in 

Flow   Equals  One-Half  the  Diameter. 

Diameter  of 
Sewer. 

Feet  per 
Minute. 

FRACTIONAL. 

PER     100. 

6 

M7 

I  in      200 

.5000 

8 

144 

I    "      280 

3571 

9 

142.5 

I    "      320 

3125 

ID 

141 

I    "      360 

2777 

12 

138 

I    "      450 

2222 

15 

134 

I    ' '      600 

1666 

i8 

129 

I    "      760 

I315 

20 

126 

I    "      890 

II23 

2» 

120 

I    "  1,160 

0862 

106  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

Main  outlet  sewers  lying-  beyond  the  point  where  houses 
are  connected  with  the  sewers,  and  which  may  safely  work 
under  lig^ht  pressure  at  times,  may  have  a  lower  inclination. 

Where  it  is  impossible  to  secure  the  grades  above  given, 
special  precaution  should  be  taken  to  keep  the  sewers  free. 
Low  g-rades  have  been  adopted  in  many  cases  as  a  choice  of 
evils,  and  by  special  precautions  have  been  made  to  serve  a 
g-ood  purpose.     The  following  are  examples: 

"At  Wave  Crest,  Rockaway,  L  I.,  a  four-inch  sewer  has  been  laid  across 
a  salt  marsh  for  a  distance  of  2,800  feet.  This  small  pipe  is  nearly  level,  the 
total  fall  being  only  three  inches;  yet,  during  the  nine  years  in  which  it  has 
been  in  use  no  stoppages  have  occurred,  and  no  trouble  of  any  sort  has  been 
met  with.  There  are  twenty-three  houses  on  this  line  of  pipe,  most  of  which 
have  their  water-closets  and  one  or  two  bath  tubs.  A  flush  tank  at  the  end  of 
the  line  of  pipe  is  supplied  by  means  of  a  windmill." — Andrezos  in  N.  Y.  State 
Board  of  Health. 

Undoubtedly,  from  the  facts  above  given,  the  lower 
levels  of  this  sewer  work  under  a  head,  at  least  during  por- 
tions of  the  time,  and  the  velocity  is  induced,  not  by  the  fall 
divided  bv  the  length  (  aioo ),  but  by  a  certain  head  greater 
than  .25  divided  by  the  length. 

A  main  sewer  in  Kalamazoo,  Mich.,  has  a  fall  of  but  1  in 
1,200  for  a  distance  of  7,-1:00  feet.  The  lower  5,000  feet  of  this 
sewer  is  twelve  inches  in  diameter,  and  the  upper  2,-1:00  feet 
is  ten  inches  in  diameter.  The  discharge  is  ordinarily  at  a 
rate  of  about  250  gallons  per  minute  at  its  maximum,  as 
taken  by  weir  measurement.  Theoretically,  this  should  fill 
the  twelve-inch  pipe  about  half  of  its  vertical  diameter,  and 
the  ten-inch  pipe  about  two-thirds  of  its  verticjil  diameter. 
Actually  the  sewer  is  often  full  nearly  to  its  crown. 

This  sewer  has  been  in  use  sixteen  years,  and  there  has 
been  no  serious  diificulty.  There  is  a  tendency  toward 
deposits,  however,  but  as  the  sewer  has  few  connections  on 
this  portion  of  its  length,  any  tendency  of  this  kind  resulting 
in  decreased  sectional  area  sets  the  sewage  back  until  the 


CHAP.    VI.  LAWS    Ol'^    I-'LOW    IN    SICWICRS.  107 

I 

head    thus    g-ained     induces    a     velocity     which     effectively 
removes  all  deposits. 

Neither  of  these  cases  then,  can  be  considered  as  war- 
ranting- us  in  adopting-  these  grades  for  a  sewer  which  is  to 
be  tapped  throughout  its  length  by  house  branches,  and 
whose  crown  should  have  air  space  for  ventilation. 

If  we  assume  a  minimum  velocity  of  180  feet  per  minute 
for  house  drains,  the  theoretical  inclination  under  the  above 
supposition  (running  half  full)  would  be  one  in  ninetv-two 
for  a  four-inch  sewer.  A  sewer  of  this  diameter  and  grade, 
running  half  full,  would  discharge  7.85  cubic  feet  per  min- 
ute. If  we  assume  it  to  be  used  by  a  family  of  six  persons, 
using  75  g-allons  per  head  per  diem,  the  total  per  diem  dis- 
charge becomes  -t50  gallons.  Assuming  the  maximum  rate 
of  discharg-e  at  150  per  cent,  of  the  mean  rate,  the  maximum 
discharge  becomes  .06*^-1:  'cubic  feet  per  minute,  or  only 
eight-tenths  of  one  per  cent,  of  the  volume  necessary  to 
secure  the  assumed  velocity  of  180  feet  per  minute  at  the 
g-rade  of  1  in  9:2.  The  assumed  velocity  would  only  be 
reached  in  the  case  of  a  four-inch  pipe,  laid  at  a  grade  of  1  in 
92,  as  assumed  above,  by  increasing  the  number  of  users 
from  6  to  750. 

The  actual  maximum  velocity  obtained  in  the  sewer 
when  used  by  six  persons,  as  above,  is  somewhat  less  than  .3 
its  velocity  when  running  half  full,  or  54  feet  per  minute. 

It  is  evident  that  in  ordinary  cases  a  g-rade  of  1  in  Iti'  in 
house  drains  will  not  be  sufficient  to  prevent  the  stranding 
of  solid  matters.  Foui--inch  house  sewers  should  have  a 
grade  of  1  in  60,  at  least,  and  ordinarily  of  1  in  48,  and  unless 
this  can  be  obtained  special  precautions  should  be  taken 
against  stoppage.  It  is  evident  from  an  inspection  of  Table 
XIV  that  a  sewer  of  six  inches  in  diameter  laid  at  the  same 
grade,  though  having  a  greater  velocity  when  working  up  to 
its  capacity,  would  in  this  case,  where  the  volume  of  flow  is 


108  the:  separate  .system  of  sewerage. 

limited,  g"ive  results  inferior  to  a  4-inch  sewer  so  far  as  the 
prompt  removal  of  sewag^e  is  concerned. 

Graphical  Solution. — A  g'raphical  indication  of  the  rela- 
tions of  the  extent  of  the  system,  tributary  population,  dis- 
charg-e,  inclination  and  velocity,  thoug-h  g-iving-  but  approxi- 
mate results,  is  much  more  convenient  in  use  than  the  most 
extended  tables.  It  makes  the  relation  of  the  several  factors 
more  apparent  to  the  eye,  and  assists  in  g^iving-  the  system  a 
proper  balance.  It  is  sufficiently  accurate  for  all  ordinary 
computations. 

A  diag"ram  showing"  at  a  glance  the  relation  of  these  fac- 
tors, and  by  which  may  be  solved  graphically  and  in  their 
proper  order,  the  problems  presented  will  be  found  on  oppo- 
site page. 

The  diagram  is  based  upon  the  supposition  that  the 
depth  of  flow  equals  one-half  the  diameter  at  the  time  of  aver- 
age maximum  daily  flow,  which  is  assumed  at  150  per, cent, 
of  the  mean  daily  flow  for  the  twenty-four  hours,  or,  a  maxi- 
mum rate  of  discharg^e  equal  to  the  discharg^e  of  the  sewag"e 
of  twenty-four  hours  in  sixteen  hours. 

This  relative  maximum  rate,  though  somewhat  below 
that  assumed  by  some  authorities,  will  seldom  be  exceeded 
in  American  cities,  where  water  is  freely  used,  and  where 
the  waste,  which  is  less  intermittingly  discharged  than 
water  legitimately  used,  is  a  large  proportion  of  the  sewag^e. 

The  following  table  exhibits  approximately  the  maxi- 
mum rate  in  several  cases,  expressed  in  terms  of  the  time 
required  for  the  discharge  of  twenty-four  hours'  sewage: 


Copyri 
Geo.  S.  P 


GRAPHICAL  SEWER  CALCULATIONS. 
BASED  ON  Baldwin  Latham's  Tables,  KunER's  Formula  and  Original  Calculations. 


£-.1 

s       °- 

-: ^ 

— 

"T 

sjI 

— 

— 

— 





— 1 

?  1 

1? 

Gallons  per  Uiem     | 

Fall  in  100 

SUrk-i-tmLPiiHiit    IMU.t          j 

ucl,  100  Fl,  of  Sew 
|g    S     S    g    S 

per 

, 

ToUl 
Gallons 
per  Olem 

Fall  in  100 

5S 

s 

g   g   s 

-.          -         .o         ,         „ 

r^'^''S52"3"SS5SS 

-.       ^      „       ,.      .-, 

-T 

-T 



— 

60,000 

~-x- 

5 

^ 

u 

-1 

. 

500,000 

^^'  !  ■' 

iOO 
1,000 

— 

— 

- 

^; 

/ 

:C 

— 

^ 

^ 

100,000 

,v    '^ 

-  ^ 

3 

~- 

.= 

^^ 

=^ 

-^' 



— 

— 

— 

— 

F 

1,000,000 

-C 

1,500 

tfm 

■^ 

^ 

x; 

?^ 

•^            1,500 
2.000 

^ 

y 

7- 

7 

y 

200,000 
250,000 

77 

"? 

< 

== 

■-4 

=:- 

=fc 

= 

;3^ 

'^^^ 

— 

■= 

^\  2,000,000 

\ps 

\7^ 

7 

\^ 

>^ 

J 

•> 

L_ 

_ 

^ 

1      - 

2,500.000 

ji_ 

\  ' 

<£- 

— 

— 

~ 

7 

1                 3,000 

li 

/ 

300,000 

Vv 

H/^ 

^ 

/ 

^ 

■--.- 



' 

3,000,000 

\  '  ' 

^ 

■■ 

^, 

/[// 

//■           3,600 

^1      /t    , 

350,000 

\  ^ 

\^ 

\ 

<f'^ 

^^ 

^_ 

"^ 

3,500,000 

l\ 

4,000 

/ 

7 

2 

? 

r'     ,000 

'   /           4.500 
/               S.OOO 

/I/I  r. 

(00,000 

\ 

h) 

•<! 

h 

"v. 

^ 

-_^ 

4,000,000 

tso.ooo 

\l 

V 

\ 

/ 

\ 

k^ 

■^ 

'0 

/ 

^- 

4.500,000 

\^ 

s 

/ 

/t 

/ 

/ 

/ 

500,000 

p 

1 

V 

k 

^ 

=4 

5,000,000 

\ 

— 

/ 

/ 

r 

/ 

t—j 

.          /     / 

560,000. 

\  \ 

\' 

s 

\' 

^ 

w 

5,500,000 

Ij 

A' 

Y^ 

7 

h 

% 

77) 

1             6,000 

7 

/ 

/ 

600,000 

1 1-  - 

\\- 

\ 

\. 

^ 

■--■ 

6,000,000 

0 

^ 

' 

/ 

^ 

7^-/1 

/ 

/ 

/  ./I  ,, 

660,000 

\ 

\ 

\- 

\ 

\'i 

^ 

^-^ 

^ 

6,500,000 

V 

-1 

T  /7 

/          J.ooo 

_i 

/ 

/i 

700,000 

\\ 

k 

\ 

k 

^ 

7,000,000 

'Vi\ 

/    /  / 

7            ,,500 

1  i/"yn 

750.000 

\ 

7 

k- 

\ 

^ 

>^ 

7,500,000 

.ItIAj 

/\  \l 

/ 

/   /             8,000 

/ 

/ 

800,000 

w 

^  \ 

^- 

?7 

^ 

8,000,000 

\^  \r. 

h 

17 

/ 

/ 

/  /           8,500 

/ 

050,000 

\\ 

\ 

\A' 

\ 

/ 

8,500,000 

v»  §\ 

^ 

-r 

r 

'" 

/ 

-H 

/    /              9,000 

, ' 

/ 

' 

900,000 

y 

\ 

r 

N 

^ 

\ 

/ 

9,000,000 

^ 

Ti 

/ 

//           9,500 

// 

/ 

950,000 

\ 

'  \ 

, 

1 

\ 

--N 

^ 

/ 

9.500,000 

\ 

1 

/ 

/ 

/  /           10,000 

/ 

/ 

/ 

1,000,000 

A 

^ 

\^ 

/ 

\ 

■^^ 

10,000.000 

1 

\ 

1 

\ 

10,500 

1 

/ 

/ 

/  /  1          10,500 

/ 

/ 

// 

1.050,000 

'  \ 

_ 

_\ 

_/ 

■s. 

N 

/>^ 

10,500,p 

f 

1 

\ 

11,000 

1 

/I 

// 

1/  /           11,000 

/ 

/ 

1,100,000 

rV 

r 

\ 

V 

7 

\ 

/ 

- 

11,000,000 

I 

\ 

/ 

1 

/ 

/ 

/ 

I 

^ 

/ 

Y 

11,500,000 

I 

\, 

ll!,00t 

1 

fh" — ^ 

/  //           12,000 

/ 

/ 

/ 

1,200,000 

\ 

\ 

-\ 

/ 

Lin 

sin 

red 

^.mp(l/ed 

fron 

\ 

12,000,000 

1 

\ 

1 

J 

/ 

/  /  / 

1  \ 

\ 

|K,M 

ula 

HSU 

tllllf 

"— 

013, 

ii"j 

1 

\ 

13,00( 

7 

7 

1/ 

/  /  /           13.00 

7 

TTlT 

1,300,00 

\ 

A 

" 

- 

7 

\ 

\ 

~ 

~ 

~ 

13,000,000 

V 

ST 

- 

13,S0( 

/ 

/ 1/  /            13,50 

/ 

, 

\ 

/ 

13,500,000 

i 

U,0OI 

/ 

11             U,00 

/ 

/ 

1,400,00 

\ 

7 

k 

\ 

/ 

.„,„ 

h, 

14,000,000 

\ 

f 

U,50l 

l'''l 

0 

7 

//              IWOI 

/ 

i 

\\\ 

1,450,00 

\ 

t 

L 

\ 

\ 

/ 

»-"■ 

14,500,000 

i\ 

\ 

1 

Mm 

./!/ 

Ji 

/v 

/               15,001 

/i/l/ 

1,500,0001        11 

\ 

\ 

N 

15,000,000 

\ 

1 

_[ 

") 


CHAP    VI. 


LAWS    OF    I-'LOW    IN    SEWERS. 


109 


TABLE  XVII. 

SHOWING    MAXIMUM    RATE    OF    SEWAGE    FLOW. 


Gaugings  Taken  at 


St.  Louis,  Mo. 


Burlington,  Vt. 

Memphis 

Kalamazoo,  .    . 


Time  of  Discharge  of  Twenty- 
Four  Hours  Sewage  at 
Maximum  Rate. 


14-3 

i8  6 

17.6 

16.4* 

19.7 

17.25 


hours. 


*Eliminating  bub-soil  water  upon  the  supposition  made  on  page  86. 

Upon  the  assumption  previous!}'  made,  that  the  maxi- 
mum rate  of  discharge  for  the  year  may  reach  twice  the 
mean  daily  discharg^e,  the  maximum  rate  for  the  year  will  be 
one-third  greater  than  that  g^iven  in  the  table. 

The  following-  is  a  comparison  of  the  conditions  of  mini- 
mum, mean  and  maximum  daily  discharg^e,  and  of  the  maxi- 
mum discharg-e  for  the  year  represented  by  60,  100,  150  and 
200  per  cent,  respectively,  as  appears  consistent  from  the 
investiirations  made: 


Discharge. 

Depth  of  Flow  in 
Terms  of 
Diameter. 

Velocity  in  Terms 

of  V.  when  Half 

Full. 

PER   CENT. 

Minimum  Daily, 6o 

Mean                "          loo 

Maximum       "          150 

Maximum  Yearly 200 

•^9 
■39 
.50 
.60 

.82 

.92 

I.OO 

1.05 

The  total  theoretical  capacity  becomes  300  per  cent., 
which  is  equal  to  a  marg-in  of  fifty  per  cent,  above  the  g-reat- 
est  anticipated  discharg-e.  This  would  not  be  realized  in 
practice,   as   the   effect  of  numerous   Y  branches  near  the 


110  THE    SEPARATE    SYSTEM    OF    SEWERAGE, 

crown  of  the  sewer  and  the  flow  from  tributary  house  drains, 
prevent  the  stream  from  reaching-  its  theoretical  velocity. 

While  the  margin  allowed  by  the  above  supposition  for 
extraordinary  conditions  is  but  about  fifty  per  cent,  of  the 
g"reatest  anticipated  flow,  it  will,  except  in  extreme  cases,  be 
found  ample.  It  should  not  be  increased  without  reason,  as 
this  will  impair  the  efficiency  and  cleanliness  of  the  system 
during-  the  ordinary  use. 

The  diagram  is  based  upon  the  tables  of  Baldwin 
Latham  and  the  formula  of  Ganguillet  and  Kutter.  The 
curves  in  black  being  computed  from  the  formula  of  Weis- 
bach. 

>/2gh  (Eq.  2) 


J^ 


in  which  //  =  head. 

/=]ength  of  pipe  in  feet. 

^=  diameter  of  pipe  in  feet. 

z/  =  velocity  in  feet  per  second,  when  running  full  or 

half  full. 
c=  coefficient  of  friction  in  pipe. 
g  =  coefficient  of  resistance  for  entrance. 

.016921 
c=.  011311 H 

e  is  assumed  at  an  average  of  ..50.5. 

The  coefficient  of  resistance  for  entrance  ie)  is  not  appli- 
cable to  continuous,  long  pipes,  fed  at  various  points 
throughout  their  length.  As  it  is  usual,  however,  to  place 
man-holes  at  intervals  along-  the  sewer,  the  coefficient  may 
properly  be  considered. 

The  curves  in  red  are  computed  from  the  formula  of 
Ganguillet  and  Kutter. 


CHAP    VI.  LAWS    OF    FLOW    IN   SFWKRS.  Ill 

r=    '— ^ VRS^Cs/RS 

in  which  €'  =  mcan  velocity  in  feet  per  second. 
6=coefficient  of  mean  velocity. 
6'=sine  of  slope. 
7?=hydraulic  mean  radius. 

;;  =  the  deg"ree  of  roug'hness  of  the  sides  of  the  con- 
duit, determined  by  experiment. 

In  computing-  the  diagram  the  value  of  ;/  is  taken  as  .018. 

It  is  probable  that  this  value  of  n  though  somewhat  above 
the  values  of  ;/  as  computed  from  gaugings  of  pipes  under 
favorable  conditions  is  a  fair  value  for  sewers  having 
branches  at  intervals  which  considerably  interfere  with  the 
continuity  of  the  current. 

The  formula  of  (Tanguillet  and  Kutter  was  elaborated 
from  gaugings  made  in  open  channels. 

It  is,  however,  undoubtedly  applicable  to  a  wider  range 
of  work  than  any  of  the  older  formulas  and  is  fairly  satisfac- 
tory when  applied  to  sewers  of  small  size. 

In  order  to  properh*  apply  the  formula  it  is  necessary  to 
know  the  value  of  ;/  where  similar  physical  conditions  prevail 
and  in  order  to  extend  the  usefulness  of  the  formula  as 
applied  to  sewers  the  following  table  is  extracted  from  a 
larger  table  g^iven  in  the  translation  of  the  "Flow  of  Water  in 
Rivers  and  other  Channels — Ganguillet  and  Kutter,"  by 
Rudolph  Hering  and  J.  C.  Trautwine,  Jr.  From  the  table 
values  of  >i  for  conditions  similar  to  those  for  the  work  in 
hand  can  be  determined. 

It  is  to  be  hoped  that  in  the  near  future  gaug^ings  of  pipe 
sewers  will  be  extended  so  that  results  may  be  tabulated 
more  closeh^  applicable  to  work  of  this  class. 

The  following  extracts  from  the  work  of  Ganguillet  and 
Kutter  are  g^iven  for  the  purpose  of  throwing  more  light 
upon  the  applicabilitv  of  the  formula  to  sewers. 


TABLE 

SHOWING    THE    VALUES    OF    II    AS 
PIPES. 


Earthenware   Pipe. 

Flowing  partly  under  a  slight  head 


Sheet  Iron  Rivited  Pipe 

At  North  Bloomfield,  funnel  mouthpiece. .  |H.    Smith  Jr.,  1876 


AUTHORITY. 


Bidder,  1853. 


New  Cast  Iron   Pipe. 


New  Cast  Iron  Pipe,  Sudbury  Conduit. 
Coated  with  Asphalt , 


Darcy,  185 1, 


Stearns,  li 


Length  in 
Feet. 


2310 


700 


365 


365 


1747 


OPEN 


Sudbury  Conduit  in  Massachusetts. 

Plaster  of  pure  cement  over  brick  work  .  .  .  Fteley     &     Stearns 

1880 

Sudbury  Conduit  in  Massachusetts. 

Hard  brick,  smooth  surface,  with  mortar 
joints  well  made.  Bottom  slope,  per 
thousand,  about  o.  i6 


490 


600 


XVIII. 

COMPUTED  FROM  ACTUAL  GAUGINGS 

UNDER  PRESSURE 


Diameter  in 

Feet  or 

Greatest 

Depth. 

Mean 

Hydraulic 

Radius  in 

Feet 

A\ 

Hydraulic 
Gradient  or 
Slope  per 
Thousand 
1000  5'. 

Mean 

Velocity 

in  Feet  per 

Second 

Coefficient 
in  Formula 

7'=  tV  ^^'^ 
C. 

Coefficient 

of 
Roughness 

«. 

1-5 

•375 

2   50 

3-581 

117. 0 

.0111 

.911 

.228 

8.50 

4.712 

107. 1 

.0108 

" 

' ' 

13-34 

6.094 

no. 6 

.0106 

" 

16.95 

6.927 

III. 5 

-OI05 

' ' 

' ' 

2559 

8.659 

113. 4 

.0104 

.9105 

33-09 

10.021 

II5-5 

.0102 

.6168 

•1542 

•27 

6  73 

104.2 

.0096 

" 

* ' 

3.68 

2.487 

104.4 

.0100 

'  ' 

' ' 

22.50 

6.342 

107.7 

.0100 

'  ' 

' ' 

109.80 

14  183 

log.o 

.0099 

*' 

* ' 

145  91 

16.168 

107  8 

.0100 

1.6404 

.4101 

45 

1.472 

108  4 

.0116 

'  ' 

' ' 

1.20 

2.602 

117. 3 

OIII 

* ' 

2.10 

3-416 

116. 4 

.0112 

'  * 

' ' 

2.60 

3-674 

112. 5 

.0115 

4.00 

1.00 

.      -318 

2.616 

146.7 

.0105 

" 

' ' 

.711 

3-738 

140. 1 

.0109 

" 

' ' 

1. 221 

4  965 

142.1 

.0108 

1.849 

6.195 

144. 1 

.0107 

CHANNELS. 

3071 

1.863 

0. 1606 

2.529 

146.2 

.0114 

3-575 

2.048 

0. 1596 

2.672 

147  9 

.0114 

3768 

2.  Ill 

0.1580 

2.805 

153.6 

.0X11 

.820 

■577 

.1596 

1. 149 

119.7 

.0110 

1. 041 

•751  ■ 

.1803 

I  439 

123.6 

.0114 

I  415 

1. 016 

.0140 

-443 

"7-3 

.0108 

Ill  THK    SEPARATl-:    SYSTEM    OF    SKIWICR AGE. 

"We  have  not  j^et  found  reason  to  modify  our  first  formula.  Still  we  must 
not  neglect  to  say  that  it  contains  a  variation  of  the  coefficient  ('  which  is  open 
to  some  doubt,  namely,  a  rapid  decrease  of  C  with  decrease  of  slope  in  small 
channelswith  very  smooth  sides.  Since,  however,  we  are  not  in  possession  of 
experimental  data  for  such  channels  with  very  light  slopes,  we  are  unable  to 
investigate  as  to  whether  our  misgivings  are  well  founded." 

"The  coefficient  n  covers  not  only  the  mere  roughness  of  the  surface,  but 
also  the  irregularities  and  imperfections  of  the  bed  of  the  channel  or  river;  it 
includes,  further  the  effect  of  loss  of  head  or  energy,  in  moving  detritus  or  silt 
along  the  bed,  in  shifting  the  main  channel  or  current  from  one  side  to  the 
other  of  the  bed,  and  in  forming  eddies  or  other  lateral  and  irregular  currents; 
in  short,  it  embodies  all  conditions  causing  retardation  of  flow,  the  relative 
effect  of  which  must  be  left  to  the  judgment.'.; 

It  should  be  borne  in  mind,  that  ;/  is  to  some  extent 
dependent  on  the  hydraulic  mean  radius.  For  the  same  con- 
ditions of  perimeter  it  decreases  as  the  hydraulic  mean 
radius  increases, 

"The  coefficient  of  resistance  or  roughness  can  be  found  only  by  consulting 
cases  where  analagous  physical  conditions  prevail,  and  for  which  its  value  has 
already  been  ascertained.  In  doing  this  we  must  consider  the  effect  of. future 
contingencies  upon  the  condition  of  the  channel  in  question,  such  as  the  wash- 
ing in  of  detritus,  etc." 

From  an  examination  of  diag"rams  by  Edmund  B.  Wes- 
ton, in  Transactions  of  the  American  Society  of  Civil  Eng^i- 
neers,  January,  1890,  comparing"  the  coefficients  of  friction  in 
pipes  as  computed  from  a  large  number  of  actual  gaugings 
of  pipes  having  interior  sides  similar  to  new  cast  iron  pipes, 
it  appears  that  the  values  of  ;/  in  Kutter's  formula  for  the 
pipes  in  question,  lie  mainly  between  the  limits  w  =  .010  and 
«=:.(>12  and  in  the  majority  of  cases  approximately  w  =  .011. 

The  value  of  C  varies  widely  for  different  values  of  n  as 
will  be  seen  by  an  examination  of  Table  XVIII.  It  may  be 
remarked,  however,  that  this  is  precisely  the  feature  which 
makes  the  formula  applicable  to  such  a  wide  range  of  work 
and  that  the  effort  to  embod}-  in  a  formula  a  variable  to 
which  can  be  given  a  value  according  with  the  condition  of 
the  channel  is  a  step  decidedly  in  advance. 


CHAP.  VI.  LAWS    OF    ]''LOW    IX    SKWICKS.  115 

Since  in  the  g-eneral  formula  of  Chezy 

v=CV^  (Eq.  1) 

in  which  t'  =  velocity, 

C=coefficient  determined  by  experiment. 

area 
R=. ^ 

wetted  perimeter 
head 

,5"= =  sine  of  slope. 

length 

area  circle- 

we  have  R= when  the  pipe  is  running-  full. 

circumference 
%  area  circle 

and  /?= when  pipe  is  running-  half  full. 

^  circumference 
The  velocity  (z')  is  the  same  when  the  depth  of  flow  is 
one-half  the  diameter  as  when  the  pipes  are  running-  full. 

When  the  depth  of  flow  is   half  the    diameter   the   dis- 
charg-e  in  cubic  feet  per  minute  becomes 
-d'    ]  ^d' 

V=30z (Eq.  3) 

4       )  4 

Assuming-  the  sewag-e  of  twent3^-four  hours  to  be  dis- 
charg-ed  in  sixteen  hours,  the  daily  capacity  in  g-allons  of  a 
sewer  under  the  condition  named,  becomes 

yi-lv^mx - —  y  X 60 X 16 X 7.48 
(  O 

in  which  2:'  =  velocity  in  feet  per  second. 
^=  diameter  in  feet; 
or, 

>^-^— X  60  X-_lil_    -X  60X16X7.48  (Eq.  4) 

(60  4       ) 

in  which  T"=  velocity  in  feet  per  minute. 
Z^  =  diameter  in  inches. 


116  THE  skpakatp:  system  of  sewerage. 

The  expression  reduces  to  the  following'  form: 

Daily  capacity  in  g-allons  =  19.5822  X  V D""      (Eq.  5) 

If  we  represent  the  inclination  and  discharg-e  g^raphi- 
cally,  by  the  abscissa  and  ordinate  respectively,  of  a  co-ordi- 
nate system,  the  value  of  the  ordinate  corresponding-  with 
any  abscissa  can  be  determined  from  the  above  formulae.  If 
we  make  the  diameter  constant,  and  compute  for  varying" 
g-rades  and  velocities,  the  ordinates  will  determine  a  curve 
representing-  pipe  of  the  assumed  diameter.  If  we  make  the 
velocity  constant,  and  compute  for  varying-  g-rades  and  diam- 
eters, the  ordinates  will  determine  a  curve  representing-  the 
assumed  velocity. 

In  the  equations  of  velocity  and  discharge,  if  we  make  D 
constant  (the  pipes  running-  half  full)  the  hydraulic  mean 
radius  becomes  constant,  and  the  discharg-e  varies  as  the 
square   root  of  the  sine   of  the   ang-le   of   inclination,   or  as 


\ioo'  S\ 


etc.,   and   the  equation  may    be  reduced  to  the 


form: 

Discharg-e  =  Jc^;;5/^,;//X—,  etc. 

^  lOO 

The  curves  of  diameter   are,   therefor*,    parabolas   and 
pass  throug-h  the  zero  of  the  co-ordinate  system. 

When  the  depth  of  flow  is  equal  to  half  the  diameter, 

Yz  (/>'X.7854     D 

R= =  — 

>^(/>X  3.1416      1 

•-C  [p., 


•J?  _ 

Discharge  =  19. 5822  D'  ^  J— 


s 


=  19.5822  C 


CHAP.    VI.  LAWS    OF    FLOW    IX    SKWICRS.  117 

or,  the  discharg-e  varies  as  the  square  root  of  the  fifth  power 
of  the  diameter. 

The  use  of  the  g"raphical  diagram  will  best  be  illustrated 
by  a  few  examples: 

(1)  Required,  the  limiting-  length  of  a  sewer  six  inches 
in  diameter,  accommodating  fifteen  persons  using-  seventy 
gallons  each  for  every  oO-foot  lot,  the  grade  to  be  .5  per  100. 

Solution.  Note  the  point  at  which  the  curve  represent- 
ing diameter  of  sewer  six  inches  is  intersected  by  the  per- 
pendicular line  of  fall  in  100  =  . 5.  From  this  intersection 
trace  a  line  to  the  left,  preserving  the  same  relative  distance 
from  the  parallel  lines  on  either  side,  until  the  vertical  repre- 
senting seventy  gallons  per  diem  per  capita  is  reached,  then 
to  the  left  and  downward,  preserving-  the  same  relative  dis; 
tance  from  the  diverging  lines  on  either  side  to  the  column  of 
Tributary  Population,  then  horizontally  to  the  left,  preserv- 
ing the  relative  distance,  as  before,  to  the  vertical  represent- 
ing- sixtv  persons  tributary  to  each  100  feet  of  sewer  (fifteen 
persons  for  each  lot  fifty  feet  in  width),  then  downward  and 
to  the  left,  preserving  the  same  relative  distance  as  before, 
to  the  intersection  with  the  column  of  lineal  feet  when  the 
distance  required  is  read,  being  in  this  case  about  2,500  feet. 

Incidentallv  we  determine  that  the  total  discharge  is 
105,000  gallons  per  day,  and  the  total  assumed  population 
1,500,  by  noting  the  point  at  which  the  line  we  traced  crossed 
these  columns  in  the  table. 

(2)  Required.,  the  size  of  outfall  necessary  to  discharge 
the  sewage  of  12,500  lineal  feet  of  tributary  lateral  sewers, 
allowing  ten  persons  for  each  twenty-five  foot  lot,  and 
seventy-five  gallons  per  diem  per  capita. 

Solution.  Starting  at  the  left  hand  column  in  the  table 
at  12,500  lineal  feet,  follow  the  diagonal  line  upward  and 
to  the  right  to  the  vertical  line  of  eighty  persons,  thence 
horizontally  to  the  right  across  the  column  of  Tributary 
Population  (which  is  determined  to  be  10,000),  thence  diago- 


118  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

nally  upward  and  to  the  rig-ht  to  the  vertical  line  of  seventy- 
five  g'allons  (midway  between  seventy  and  eig"hty),  thence 
horizonteilly  to  the  rig-ht,  when  we  note  that  the  total  daily 
discharge  will  be  750,000  gallons,  and  that  it  will  require  a 
sewer  of  the  following  dimensions: 

20  inches  in  diameter  ...  .05  per  100  g"rade. 
18  inches  in  diameter  ...  .11  per  100  grade. 
15  inches  in  diameter  ...  .26  per  100  grade. 
12  inches  in  diameter  ...  .75  per  100  grade. 
10  inches  in  diameter  . .  ..1.S8  per  100  grade. 

But  from  the  curves  of  velocity  we  note  that  the  20-inch 
sewer  laid  at  a  grade  of  .05  per  100  has  a  velocity  less  than 
120  feet  per  minute,  which  is  inadmissible,  and  the  18-inch 
sewer  laid  at  a  grade  of  .11  per  100  has  a  velocity  of  scarcely 
120  feet  per  minute  (118  by  arithmetical  computation),  and 
the  minimum  velocity  we  have  assumed  in  Table  XVI  is  129 
feet  per  minute.  The  conditions  will  be  met  by  either  of- the 
other  three  sewers,  and  the  velocity  in  each  case  will  be 
approximately  170  feet,  240  feet  and  390  feet  per  minute. 

(3)  Required^  the  size  of  outfall  sewer  to  accommodate 
a  population  of  100,000,  using  seventy  gallons  per  diem  per 
capita. 

Solution.  We  observe  that  15,000  is  the  greatest  num- 
ber provided  for  in  the  column  of  Tributary  Population.  At 
the  right,  however,  will  be  found  a  supplementary  diagram, 
in  which  the  gallons  are  ten  times  the  corresponding-  number 
of  gallons  in  the  main  diagram.  We  can,  therefore,  use  that 
part  of  the  diagram  to  the  left  of  the  column  marked  "total 
gallons  per  diem"  in  connection  with  the  supplementary 
table,  by  multiplying-  "lineal  feet  of  sewer"  or  "tributary 
population"  by  10.  Starting  thus  at  10,000  in  the  column  of 
tributary  population,  trace  the  line  upward  and  to  the  rig-ht, 
to  its  intersection  with  the  vertical  representing-  ninety  gal- 
lons, thence  horizontally  to  the  supplementary  table,  we  read 


CHAP.    VI.  LAWS    OF    FLOW    L\    SKWISKS.  110 

9,000,000  g"allons  daily,  and  continuing-  the  horLzontal  line  we 
cross  the  sewers  of 

54  inches  in  diameter  at  .06  per  100  g^rade. 
48  inches  in  diameter  at  .11  per  100  grade. 
40  inches  in  diameter  at  .26  per  100  grade. 
36  inches  in  diameter  at  .44  per  100  grade. 
Either  one  of  these  sewers  laid  at  the  grade  indicated 
will  till  the  conditions. 

(4)  Required^  the  number  of  people  using-  sev^enty-five 
g-allons  per  diem  each,  that  can  be  served  by  a  4-inch  house 
drain,  laid  at  a  grade  of  2  in  100. 

Sohitioii.  Tracing  a  line  from  the  point  where  the  curve 
of  4-inch  diameter  is  intersected  by  the  vertical  of  grade  per 
hundred  =  2,  to  the  left  and  horizontally  to  the  vertical  of 
seventy-five  gallons,  thence  to  the  left  and  downward  we 
read  1,000  people. 

Other  uses  of  the  diagram  will  readily  suggest  them- 
selves.    Of  the  four  quantities, 

Total  gallons  per  day. 
Velocity, 
Fall  in  100, 
Diameter, 
any  two  being  given,   the  other  two  can  be  determined  by 
inspection  of  the  diagram. 

Let  us  take  that  portion  of  the  Cit\'  of  Schenectady, 
N.  Y.,  lying  between  the  Erie  Canal  and  the  Mohawk  River, 
and  tributary  to  the  Front  street  sub-main  sewer,  as  an 
example  illustrating-  the  use  of  the  table  in  proportioning  a 
complete  system. 

The  territory  has  at  present  a  population  of  5,000,  dis- 
tributed with  tolerable  uniformity.  The  ag-g-reg-ate  length 
of  the  sewer  is  15,065  feet,- giving-  thirty-three  persons  for 
each  100  feet  of  sewer.  In  this  case  it  is  not  likely  that  the 
territory  will  ever  reach  a  g-reater  density  of  population. 
We    will    assume,    however,    that    it    may  reach    a    density 


120  THE    SEPARATK    SYSTEM    OF    SEWERAGE. 

expressed  by  fifty  persons  for  each  lOO  feet  of  the  sewer, 
and  will  assume  a  discharg^e  of  seventy-five  g^allons  per  diem 
per  capita. 

First,  arrange  the  distance  of  the  various  branches  so 
that  the  ag"g"reg"ate  leng^th  of  sewer  tributary  to  any  point  can 
readily  be  seen  on  inspection  as  follows: 
From  corner  Washington    Ave.    and   Union  St.    to  corner  of 

State  and  Church  Streets 860 

Church  —  Union  to  State 400 

1260 

State — Church  to  Ferry 440 

State — Canal  to  Ferry 530 

•  2230  2230 

Ferry — State  to  Liberty 245 

Liberty — Erie  Canal  to  Ferry 730 

3205 

Ferry — Liberty  to  Union 290 

Washington  Ave.  and  Union  to  Church 625 

Church — Front  to  Union 450 

1075 

Union^Church  to  Ferry 425 

1500       1500 

4995 

Ferry — Union  to  Front 725 

Washington  Ave.  and  Front  to  Ferry 1200 

6920 
Front — Ferry  to  College 935 

College — Liberty  to  Union   350 

Union — Ferry  to  College  ....    830 

College — Union  to  Green 665 

1845 

Green — Ferry  to  College .■ 825 

Green— R,  R,  to  College.    i75 

2845 
College — Green  to  Front 560 

3405  3405 

1 1 260 


CHAP.    VI.  LAWS    OF    FLOW    IN    SICWIOKS.  121 

Bro!ii^^/if   for-ward 1 1260 

Front — College  to  John 420 

John  Street 74° 

12420 

Front  —John  to  Jefferson 255 

Jefferson 600 

Madison    200 

800  800 

13475 
Front — Jefferson  to  Monroe 250 

13725 

Monroe 5°° 

Front — Monroe  to  outlet  main 840 

15065 

If  we  assume  the  smallest  laterals  to  be  six  inches  in 
diameter  and  the  g-rade  to  be  .5  per  100,  we  see  from  the 
diag-ram  that  their  limiting-  leng-th  in  this  case  is  2,800  feet. 
This  size  will,  therefore,  suffice  until  their  agg"regate  length 
exceeds  2,800  feet.  Should  the  g-rade  be  increased,  however, 
at  this  point  the  6-inch  sewer  may  be  extended  still  farther. 

Inspecting-  the  fig-ures  made  above,  we  determine  that 
the  size  must  be  increased  after  the  junction  of  the  Liberty 
street  and  Ferry  street  sewers.  Assuming-  the  g-rade  imme- 
diately below  this  point  to  be  A  per  100,  we  determine  from 
the  diag-ram  that  an  8-inch  pipe  will  suffice  up  to  an  ag-gre- 
g-ate  length  of  5,000  feet.  Inspecting-  the  summation  above, 
we  determine  that  this  is  reached  after  the  Ferry  street 
sewer  receives  the  Union  street  sewer  and  its  tributary 
branches.  From  this  point  then,  the  size  must  be  increased. 
Assuming  the  grades  from  this  point  to  be  .28  per  100,  we 
determine  from  the  diagram  the  limiting-  length  of  a  10-inch 
pipe  to  be  7,500  feet.  From  the  summary  of  leng-th  we  see 
that  this  would  require  a  still  g-reater  increase  of  size,  the 
grade  being-  the  same,  355  feet  above  the  junction  of  the  Col- 
lege street  sewer.      A  man-hole  at  this  point  is  not  contem- 


122  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

plated,  and  a  chang"e  in  size  between  man-holes  is  not  advisa- 
ble; we  will,  therefore,  increase  the  g-rade,  retaining-  the 
same  size.  Recurring-  to  the  diagram,  we  see  that  the 
required  g-rade,  the  diameter  being-  ten  inches  and  the  ag^g-re- 
g-ate  leng-th  being-  7,  855  (or,  in  round  numbers,  8,000)  feet,  is 
.32  per  100.  The  g-rade  from  a  point  355  feet  above  College 
street,  will,  therefore,  be  increased  to  .32  per  100. 

Taking  up,  now,  the  branches  tributary  to  the  Colleg-e 
street  sewer,  and  remembering-  that  our  limiting  distance 
for  the  smaller  laterals  is  2,S00  feet,  we  note  that  the  size 
must  be  increased  at  the  junction  of  the  Green  street  sewer. 
It  is  evident  that  from  this  point  to  the  Front  street  main  an 
8-inch  pipe  will  be  ample. 

Uniting-  the  College  street  sub-main  with  the  Front 
street  main,  we  have  an  aggreg-ate  leng-th  of  11,200  feet. 
Assuming  the  grade  below  to  be  .32  per  100,  the  diag-ram 
g-ives  the  limiting  length  for  a  12-inch  sewer  as  12,700.  This 
is  reached  when  we  add  the  Madison  street  sewer  and  tribu- 
taries. From  this  point  the  g-rade  required  to  reach  Monroe 
street  (13,375  feet,  ag-greg-ate  distance),  we  find  by  the 
diag-ram  to  be  .36  per  100,  and  to  reach  the  main  outlet 
(15,0(35  feet,  ag-g-reg-ate  distance),  .14  per  100,  the  size  of 
sewer  being-  maintained  at  twelve  inches.  Incidentally  we 
note  that  the  velocity  at  this  point  is  two  hundred  feet  per 
minute,  and  the  daily  discharg-e  565,000  gallons. 

If  the  formula  of  Kutter  is  preferred  the  procedure  is 
precisely  similar,  using-  the  red  lines  instead  of  the  black 
ones. 

The  computations  can  be  made  with  the  same  facility, 
commencing  at  the  outlet  and  proceeding-  toward  the  dead 
ends.  A  comparison  of  the  results  obtained  from  the  dia- 
g-ram by  different  persons  show  them  to  ag-ree  within  about 
one  per  cent.,  an  error  of  no  consequence  when  the  data  can- 
not be  stated  with  precision. 


CHAP.    VI. 


LAWS    OF    FLOW    IN    Si: WICKS. 


123 


It  is  proper  to  state  that  Baldwin  Latham,  in  calculating- 
the  tables  on  which  the  diag^ram  is  based,  has  assumed  a 
value  for  h  equal  to  the  velocity  in  feet  per  second  in  each 
case,  to  simplify  the  computations.  The  tables  are,  there- 
fore, stricth'  correct  only  when  the  leng-th  in  feet  equal  the 
velocit}^  in  feet  per  second;  multiplied  by  the  denominator  of 
the  fractional  inclination.     Thus: 

n  200 490  feet. 

n  100 355  feet. 

n  400 5)80  feet. 

n  200 710  feet. 

n  1000 2166  feet. 

n  5000 1575  feet. 


6-inch  pipe,  g-rade  1 

6-inch  pipe,  grade  1 
12-inch  pipe,  g^rade  1 
12-incb  pipe,  g-rade  1 
24:-inch  pipe,  g-rade  1 
21:-inch  pipe,  g-rade  1 

Comparison  of  Various  Standard  Formulae. — Some 
authorities  prefer  to  use  other  formuke  than  those  of  Weis- 
bach,  on  which  the  diag-ram  is  based.  A  comparison  of  the 
results  obtained  from  various  standard  formulae  is  presented 
below. 

The  following  are  some  of  the  standard  formulee  used 
by  the  best  authorities: 

_      n/2o7/ 

^l+r+/: 
1.S113 


Baldwin  Latham,  J 
Weisbach,  \ 

I  w.m 

Kutter, . .  r'=  -   


■  d 

.002807 


S 


.002807       n 


y/RS  =  Cs/  RS 


in  which  t'  =  mean  velocity  in  feet  per  second. 

C=  coefficient  of  mean  velocity. 

iS'=sine  of  slope. 

y?=hydraulic  mean  radius. 

;/  =  deg-reeof  roug-hness,  determined  by  experiment. 
Beardmore, ....  z'=lOOs/  R^ 
Eytelwein, v  —  \Y?,Ax^  Rs 


12-i  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 


Box 


Shone,  )  ''  373. 98^ 


in  which   fl!'=diameter  in  inches. 
Zr=head  in  feet. 
Z=leng-th  in  yards. 
a  =  sectional  area  in  square  feet. 

. — 

N'.00371(^+1)Z 
in  which   ^=  diameter  in  inches. 
//=head  in  feet. 
Z,  =  leng-th  in  feet. 

From  these  formula?  the  following-  table  has  been  com- 
puted: 


CHAP.    VI. 


LAWS    OF    FLOW    IN    SKWFKS. 


125 


TABLE  XIX. 

COMPARING    THE    DISCHARGE    IN    THE   VARIOUS    CASES    AS    GIVEN    BY    DIFFERENT 
STANDARD    FORMULA. 


B  - 


KUTTER. 


«=       n 
.013       .015 


6 

•50 

6 

2.00 

12 

•25 

12 

1.50 

18 

.14 

18 

1.00 

24 

.10 

24 

.50 

DISCHARGE  IN  CUBIC  FEET. 


28.81 
60. 17 
115  40 
294  90 
236.50 
660.90 
408.50 
958.30 


25.68 

21. I 

51 36 

42.2 

132.00 

102.0 

318  00 

272.0 

294.00 

234  0 

762.00 

618.0 

516.00 

420.0 

1, 170  00 

9540 

16.80 

33  60 
83  40 
203.85 
191  97 
513  00 
35800 
801.00 


29.4 

58.8 

118  0 

288.4 

243  0 

649  0 

421-5 

942.6 

27.69 

55.38 

no  90 
270  go 
229.00 
612.00 
398.00 
888.00 


27.0 
54.2 

108.4 


223.0 


30.9 
61.8 

128 

315 
264 

718 
472 
,056 


PERCENTAGE  RELATION. 


6 

■50 

6 

2.00 

2 

•25 

2 

1.50 

8 

.14 

8 

1. 00 

4 

.10 

4 

.50 

100 
100 
100 
100 
100 
100 
100 
100 


89 
85 

114 

107 

124 

115 

126 

123 


73 
70 
88 
92 
99 
94 
103 

TOO 


68 
56 
72 
69 
81 

79 

88 

83 


102 
98 

102 
98 

103 
98 

103 


96 
92 
96 
92 
97 
93 
98 

93 


94 
90 

94 


94 


107 
103 
112 
107 

112 
109 
116 


126  THE    SEPARATE    SYSTEM     OT^    SEWERAGE. 

It  will  be  observed  that,  with  the  exception  of  Kutter's 
formula,  the  results  above  g"iven,  thoug-h  not  equal,  run 
approximately  parallel. 

Kutter's  formula  g^ives  much  smaller  values  for  sewers 
of  small  diameter,  and  much  larger  values  for  sewers  of 
larg-e  diameter.  When  w  =  15,  the  values  g^iven  by  Kutter 
and  Latham  are  approximately  equal  for  a  sewer  five  feet  in 
diameter.  This  value  of  ;/,  however,  is  not  applicable  to 
vitrified  pipe  sewers,  well  constructed,  unless  it  be  on  verv 
sharp  curves,  where  ordinarily  the  work  is  less  perfect. 

Loss  of  Head  on  Curves. — An  increase  of  inclination 
should  be  given  around  curves,  both  to  overcome  the 
increased  friction  due  to  ang-ular  chang"e  in  direction,  and 
also  for  the  reason  that,  as  ordinarily  laid,  there  is  a  slig^ht 
opening"  of  the  joints  in  the  outward  circumference  and 
g-reater  liability  to  stoppag^e  from  articles  lodg-ing-  crosswise. 
The  allowance  indicated  by  theory  for  the  increase  of 
friction  on  curves  is  not  sufficient,  for  the  reason  that  pipes 
are  not  usuall}^  laid  so  truly  to  line  or  g-rade  as  when  laid  in 
straig-ht  lines,  and,  aside  from  the  increased  friction  due  to 
the  angular  chang-e  in  direction,  we  may  properly  increase 
the  coefficient  of  resistance  to  flow  in  the  pipe. 

The  following-  is  Baldwin  Latham's  modification  of  Weis- 
bach's  formula  for  loss  of  head  due  to  ang^ular  friction: 

/^  =  head  necessary  to  overcome  ang^ular  friction. 

z'  =  velocit3^  in  feet  per  second. 

(/  =  angle  in  deg^rees. 

r=  radius  of  pipe. 

/."^radius  of  the  bend. 
2^=64.38. 

^^coefficient. 


a       V 
h  —  cV.  —  X —  or, 
90     2^ 


CHAP.    VI. 


LAWS    OF    FLOW    IN    SICWIOKS. 


127 


■X^?Xf 


579.4 
In  which  r=.  131X1.847 


(Eq.  6) 


M 


/> 

.2 

■3 

■4 

.5      1      .6 

•7 

.8 

•9 

I.O 

<  =  .i3i 

.138 

.158 

.206 

.294       .440 

.661 

•977 

1.408 

1.978 

Assuming-  a  6-inch  sewer  laid  with  a  curve  of  fifty  feet 
radius,  the  ang^le  of  the  curve  being-  sixty  deg-rees,  or  its 
length  52.4  feet,  and  tlie  velocity  above  the  curve  to  be  five 
feet  per  second,  the  increased  head  necessary  to  overcome 
friction  due  to  angular  change  in  direction  is,  according-  to 
equation  six,  less  than  one-eighth  of  an  inch.  In  no  case 
which  could  possibly  occur  in  curves  of  a  proper  radius  will 
the  formula  give  more  than  a  small  fraction  of  an  inch  as  the 
value  of  //.  This  is  too  small  to  be  considered  in  w'ork  of  this 
class. 

In  proposing-  a  formula  for  the  increased  head  or  inclina- 
tion required  for  curves  as  ordinarily  laid  in  sewer  work,  we 
may,  therefore,  disreg-ard  the  effect  of  ang-ular  change  in 
direction. 

If,  however,  we  assume  that  the  increased  roug-hness  of 
the  pipe  would  increase  the  coefficient  ;/,  as  g-iven  in  Kutter's 
formula,  from  ;/  =  .011,  its  value  as  g-iven  for  plaster  of 
cement  with  yz  sand,  to  ;/  =  .013  and  ;/  =  .015,  its  value  as 
g-iven  for  brick  work  and  terra  cotta  pipes  wath  imperfect 
joints  and  in  bad  order,  we  have  from  Kutter's  formula,  by 
computation,  the  following  table: 


128 


THE    SEPARATE   SYSTEM    OF    SEWERAGE. 


TABLE  XX. 

SHOWING    INCREASED    FRICTIONAL    HEAD    REQCIRED    FOR    CURVES    IN    VARIOUS    CASES. 


r=2' 

2   FEtT 

I'=5  FEET  PER 

Diameter. 

Coefficient 
of  Resist- 
ance. 

Velocity. 

age  Rela- 
tion of 
C.  * 

PER  SECOND. 

SECOND. 

Grade 
per 

IOC. 

Loss  of 
Grade 
per  100. 

Grade 
per 
100. 

Loss  of 
Grade 
per  100 

6  inch 

;/=.oii 

87  35  VA^-^ 

100.00 

.65 

.... 

2.62 

"      " 

.==.013 

69.777  A\S' 

7986 

1.02 

■37 

4  10 

1.48 

"      " 

;;=  015 

57.i5\/A\S- 

66  00 

1-53 

.87 

6.12 

3^5o 

12  inch 

//=.OII 

105  74  V  /\S 

100  00 

.22 

.89 

" 

//=.oi3 

84.927^' 

80.31 

•34 

.12 

1.38 

•49 

" 

«=.oi5 

70.8  V7^- 

66  00 

•49 

.27 

I  99 

1. 10 

i8  inch 

;/=.oii 

116. 2    V  A^' 

100.00 

.12 

•49 

..       ,. 

//=.oi3 

94  7    V^^ 

81.45 

.18 

.06 

•74 

25 

" 

;/=  015 

79.0  V^' 

68.00 

.26 

■14 

1.06 

■57 

*According  to  Kutter. 

In  the  columns  of  loss  of  grade  per  100  feet  can  be  found 
the  increased  fall  necessary,  under  the  supposition  that,  on 
ordinary  curves,  n  is  increased  from  .011  to  .013,  and  on 
sharp  curves  from  .011  to  .01.5. 

It  will  be  observed  that  when  «  =  .013  the  value  of  C  is 
decreased  to  about  eig^hty  per  cent,  in  all  cases.  Recurring- 
to  the  g-eneral  formula  of  Chezy,  which  for  the  ordinary 
rang-e  of  diameter  and  velocity,  becomes,  approximate!}'. 

We  mav  write  for  ordinarv  curves. 


z;  =  80v/i?6" 


CHAP.   VI.  LAWS    OF    FLOW    IN   SEWERS.  129 

in  which  S'= —  =  slope  required. 

/ 
From  the  preceding"  equations  we  have 

S= 


(100)'/? 

S'  = 

(80)*/? 
Or,  since  in  each  case  the  hydraulic  mean  radius  when 

the  sewer  is  half  full= — 

4 
^^' ^  — . 

1600^/        2500^ 

H—h' — //  = =  loss  of  head  required  (Eq.  7) 

In  pipe  sew^ers,  however,  the  roug^hness  is  somewhat 
dependent  on  the  ratio  of  the  radius  of  the  curve  to  diameter 
of  the  pipe. 

Empirical    Formula. — The    following"   formula  will   g"ive 
g"Ood  results  in  pipe  sewers: 
z'V    (         10^  ) 

//= 1+ \  (Eq.  8) 

iOOOrt'  {  r     ) 

in  which  z'  =  velocity  in  feet  per  second. 

/=leng-th  of  curve  in  feet. 

<f=  diameter  of  sewer  in  feet. 

r=radius  of  axis  of  curve  in  feet. 
Il—\os<,  of  head  for  curve  in  feet  due  to  increased 
roug"hness. 

^in  the  above  formula  does  not  represent  the  total  fall 
required  for  the  curve,  but  the  excess  of  fall  necessary  over 
that  if  the  sewer  were  straig^ht,  and  the  flow  had  an  equal 
velocitv. 


CHAPTER  VII. 

MATERIAL  AND  ACCESSORIES. 

Sewer  Pipes. — Salt-g"lazed,  vitrified  earthenware  is  the 
best  material  thus  far  produced  for  sewer  pipes.  It  forms  a 
smooth,  impervious  conduit,  is  not  affected  by  the  sewag-e, 
and  is  practically  indestructible.  It  is  manufactured  in  all 
sizes,  from  two  inches  to  three  feet  in  diameter,  and  in  con- 
venient forms  for  special  purposes.  It  is  also  made  of  "stan- 
dard" thickness  and  "double  streng-th."  The  pieces  are 
usually  either  two  or  three  feet  in  length.  They  are  either 
made  with  a  "bell"  at  one  end  for  holding-  the  "spigot"  end 
of  the  adjoining  piece  in  laying,  or  as  simple  cylinders,  with  a 
separate  collar  for  making  the  joint.  The  socket  and  spig^ot 
pipe  is  usually  preferred.  Pieces  with  Y  branches  should 
be  placed  wherever  a  house  drain  is  to  be  connected  with  the 
sewer. 

Tests  of  twelve-inch  sewer  pipe  were  made  at  Boston  b}' 
Chief  Engineer  W.  H.  Bradley,  with  the  following  results: 

"The  pipes  were  three  feet  long  and  without  sockets,  except  as  noted. 

"The  crushing  test  was  made  by  bedding  the  pipes,  horizontally,  half  their 
depth  in  sand  and  crushing  them  by  a  weight  applied  uniformly  along  the 
length  on  the  top;  figures  are  pounds  per  foot  of  length  (average  of  three  pipes). 

'  'The  breaking  test  was  made  by  supporting  ends  of  pipes  on  two  blocks 
two  feet  six  inches  apart  and  applying  weight  at  center;  figures  are  total  weight 
(one  test). 

"The  abrasion  test  was  made  by  applying  a  section  '2  inch  square,  loaded 
with  20  lbs.,  to  a  revolving  grindstone  three  feet  in  diameter,  kept  wet  and 
clean;  figures  are  revolutions  necessary,  ist,  to  remove  glazing;  2nd,  to  grind 
away  Vio  of  total  thickness  including  glazing  (average  of  two  tests)." 


CHAP.   VII. 


MATICHIAL    AND    ACCKS.SORIKS. 


131 


■ssaa 

t^ 

oo 

o 

in 

N 

f^      in 

rr' 

0 

o> 

o 

pn 

m 

00 

m 

O 

o> 

d 
o 

-M^Mli  oi-i 

in 

ro 

o 

in 

t^ 

J3 

< 

■SnizBio 

lO 

o 

rr' 

m 

o- 

rf        rr 

in      N 

(N 

r** 

m 

!-J 

t-~        w 

•ueds 

o 

CJ 

^ 

c- 

O         M 

rr 

c^ 

o 

o\ 

CT 

O 

c 

CT>        00 

o 

PO 

•ni  9    jj  z  no  -sqq 

N 

o- 

VO 

<N 

Cv 

c 

C 

(S 

00 

'jq'Sia^  3nt5iEaja 

^ 

rr 

tt      -^      -^      m 

■«- 

■^ 

m 

•qj3n3T 
jooj  J9d  -sqq 

t~- 

M 

t^      vO 

o       m      in      N 

0 

M 

lO 

^^ 

0 

o- 

O 

00 

Ti-      t^      CTi      in     00 

m 

CM 

00 

oo 

N 

M        00 

"3-      O 

00 

0 

m 

o 

m 

iqai9A\  3n!qsnj3 

N 

'-' 

IN 

N 

N      ►-■ 

N 

tT        m 

N 

04 

CM 

b) 

td 

s 

O 

u-1       00 

N 

M              O 

KH 

t--. 

N 

< 

CN 

01 

Ti-      m       m       ^ 

ro 

■XjiAEjQ  ogpadg 

5 

C^ 

N 

M 

04 

IN         D 

N 

N 

CM 

z 

c« 

'■O 

C\       ro       O 

i-i          CM 

^C 

o 

■r     o 

0 

in 

Ed 

■saqouj 

O^       O 

o 

O 

c 

M 

o 

O  t^ 

l_^- 

ui   ssannoiqx 

M 

O 

" 

-^ 

H 

^     - 

" 

-; 

"■ 

""      M 

X 
X 

z 

td 

> 

r^ 

PO       o 

in      in      o 

o 

^     o 

C 

»_( 

< 

J 

■jooj  jad 

•sqT  UI  }q3pA\ 

d         IN         O         O         r^        1- 
"*■        ■^       -"l-       Tl-       rj-       t: 

o      o      o 
r      -^      '*-      "*- 

-Jt 

H 

H 

EX, 

1) 
c 
o 

td 

td 
tr. 

_C 

]         4. 

o     .c 

4 

C 

O 

H 
(d 
H 

0^ 

o 
w 

i-T 

3 
o 

15 
C 

c 

C 

c 
c 

1- 

< 
> 

C 
c 

K 

o: 

C 

O     ^ 
o 
6      c 
U      <- 
m 

<v      > 
^     .- 
tJ      '^ 

3 

CQ     >. 

1 

^ 

c 

1       a 
'J- 

C 

c 

c 
7 

c 

> 

0) 
N 
CO 

0 
a 

E 

t: 
c 
a 

;- 

C 
C 

"S 
o 

XI 

ii 

cfl 

U 

IS 

-a 

o 

2 

U 
<- 
1 

■s 

< 

0    '3 

c 

c     ^ 

_c 

u 

ao 

<       I- 

u      c 

a 

C 

c 

: 

'J 

C 

> 

c 

1 
1 

lU 

tJ 

c 

00 

o 

0 

t: 

4. 

a 

0. 

T 

C 

X. 

- 

- 

t/ 

"a 

>- 
a 

o 

s 

CM 

o 

c 

e 

s 

H     ^ 

c 

a 

c 

^ 

en 

132  THE    SEPARATE   SYSTEM    OF    SEWERAGE. 

Tests  of  double  strength  sewer  pipe,  manufactured  by 
Blackmer  and  Post  were  made  b}'  H.  R.  Gates,  Superinten- 
dent of  the  Geo.  J.  Fritz  Foundry  and  Machine  Co.,  with  the 
following-  results: 

I  Section  24-inch  Double  Strength  Culvert  Pipe, 

2  inches  thick,   broke  at 27,610  pounds. 

I  Section  24-inch  Double  Strength  Culvert  Pipe, 

2  inches  thick,  broke  at 28,715  pounds. 

I    Section  27-inch  Double  Strength  Culvert  Pipe. 

2.%  inches  thick,  broke  at 33. 133  pounds. 

I   Section  27-inch  Double  Strength  Culvert  Pipe, 

254^  inches  thick,  broke  at 32,763  pounds. 

I   Section  30-inch  Double  Strength  Culvert  Pipe, 

2%  inches  thick,  broke  at 27,987  pounds. 

I   Section  30-inch  Double  Strength  Culvert  Pipe, 

2)^  inches  thick,  broke  at 24,297  pounds. 

I  Section  27-inch  Standard  Culvert  Pipe, 

2]/%  inches  thick,  broke  at 23,986  pounds. 

I  Section  27-inch  Standard  Culvert  Pipe, 

2]/%  inches  thick,  broke  at 22,530  pounds. 

I   Section  30-inch  Standard  Culvert  Pipe, 

2%  inches  thick,  broke  at 27,875  pounds. 

Internal  pressure  was  applied  with  the  following  results: 
24-inch  Culvert  Pipe  burst  at  100  pounds  pressure  to  the  square  inch, 

showing  a  horizontal  crack  on  the  side  from  end  to  end. 
27-inch  Culvert   Pipe  showed  no  weakness  of  the  material  or  in  the 

joint  at  100  pounds  pressure,  but  the  bulkheads  leaked  so  much 

that  no  more  pressure  could  be  applied. 
30-inch  Culvert  Pipe  showed  no  weakness  of  material  or  in  the  joint 

at  100  pounds  pressure,  but  the  bulkheads  leaked  so  much  that  no 

more  pressure  could  be  applied. 

In  making  the  tests  as  shown,  blocks  of  wood  were 
hollowed  out  to  fit  as  nearly  as  practicable  the  shape  of  the 
pipe,  each  block  coyering  a  little  less  than  one-fourth  the 
circumference  of  the  pipe,  the  power  being  supplied  by  a 
hand-pump,  the  pressure  being  registered  on  the  guage 
as  applied. 


CHAP.  YII.  MATKKIAL    AND    ACCESSOKIIOS.  133 

The  capacity  of  vitrified  salt-g-lazed  sewer  pipe  to  resist 
abrasion  is  very  marked. 

Hand-Holes. — A  "hand-hole"  is  a  piece  of  pipe  provided 
with  a  detachable  section.  See  Fig-.  2.  These  hand-holes 
afford  the  means  of  removing-  obstructions  without  breaking 
the  pipe.  They  are  usually  laid  at  intervals  of  about  one 
hundred  feet.  Their  use  may  be  dispensed  wath  and  the 
sewer  may  be  opened  when  necessary  by  removing  the  cap 
from  a  Y  branch. 


Fig.    2. 

Lamp-Holes. — At  intervals  a  T  should  be  placed  in  the 
sewer  and  a  stand-pipe  carried  to  the  surface,  forming  an 
opening  where  the  action  of  the  sewer  may  be  observed.  See 
Plate  I.  Part  of  them  may  stop  just  beneath  the  pavement 
and  be  covered  with  a  lig-ht  casting-,  shown  in  Plate  I,  and  at 
longer  intervals  part  of  them  may  be  carried  to  the  surface 
and  protected  with  a  cast  iron  cover. 

Fresh  Air  Inlets. — These  will  answer  in  place  of  man- 
holes in  some  cases  when  the  distance  between  the  junction 
of  two  or  more  sewers  is  considerable.  They  afford  facili- 
ties for  inspection,  and  have  the  advantage  of  preserving  the 
flow  of  sewage  in  its  proper  sectional  form  and  precluding- the 
possibility  of  deposit.  They  are,  however,  not  as  available  as 
points  from  which  cleaning  tools  can  be  inserted  into  the 
sewer.  They  should  be  covered  with  a  perforated  cast-iron 
cover,  similar  to  that  shown  in  Plate  II,  to  assist  in  the  venti- 
lation of  the  sewer.     The}'  can  be  very  cheaply  constructed. 


134  THE  sepakatp:  system  of  sewerage. 

Man-Holes. — Where  two  or  more  sewers  unite  a  man- 
hole should  be  placed.  See  Plates  V,  VI,  VII,  VIII.  Thej 
should  be  built  of  selected,  hard  brick,  laid  in  cement  mor- 
tar, plastered  outside,  and  surmounted  by  a  heavy  cast-iron 
cover.  It  is  very  difficult  to  make  a  proper  connection 
between  two  pipe  sewers  of  larg-e  size  by  the  use  of  the  ordi- 
nary Y  branch.  The  man-holes  are  also  required  for  pur- 
poses of  inspection,  repair,  removal  of  obstructions,  and 
ventilation. 

The  advisability  of  omitting-  man-holes  has  been  consid- 
erably discussed  of  late,  but  in  cases  where  they  have  been 
omitted  it  has  usually  resulted  in  their  being-  built  subse- 
quently. They  add  larg-ely  to  the  cost  in  the  Separate 
System  and  should  not  be  used  more  frequently  than  is 
necessary. 

Flush-Tanks. — All  dead  ends  should  be  supplied  with 
automatic  flushing  tanks,  the  size  of  which  should  be  propor- 
tioned to  the  size  of  the  lateral.  They  should  be  built  of 
selected,  hard  brick  and  cement  mortar,  and  plastered  inside 
and  outside,  and  surmounted  by  a  heavy  iron  cover.  They 
are  usually  supplied  with  water  from  the  street  mains 
throug-h  an  ordinary  service  pipe  of  small  size,  and  the 
admission  of  water  is  controlled  by  an  ordinary  lever  handle 
stop-cock.  They  are  built  in  various  forms  and  will  be  more 
particularly  described  in  the  chapter  on  Flushing-  and  Ven- 
tilation. 

Y  Branches. — The  usual  form  of  Y  branch  is  shown  in 
Plates  I  and  X.  It  consists,  essentially,  of  a  cylinder  of 
smaller  diameter  intersecting-  the  main  pipe  at  an  ang-le  of 
about  thirty  deg-rees,  measured  on  the  side  of  the  intersec- 
tion toward  the  socket  end  of  the  main  pipe.  The  axis  of 
the  intersecting  cylinders  meet  in  a  common  point.  The  Y 
branch  can,  therefore,  be  turned  to  the  right  or  left  with 
equal  facility. 


PLATE  II. 


DETAILS 

—  OF  — 

FRESH    AIR     INLET. 


CHAP.    VII.  MATICKIAL    AND    ACCESSORIES  137 

Another  form  of  Y  branch  is  shown  in  section  in  Plate 
I.  It  consists  of  an  intersecting-  frustum  of  a  cone,  the  diam- 
eter of  whose  base  is  equal  to  the  diameter  of  the  main  pipe 
and  common  with  it.  It  is  claimed  for  this  branch  that  it 
induces  a  more  perfect  ventilation  by  entirely  withdrawing- 
the  air  from  the  crown  of  the  main  sewer. 

It  is  open  to  the  objection  that  it  does  not  preserv^e  the 
proper  cross-sectional  form  of  the  stream  but  allows  it  to 
spread  out  laterally  into  the  branch  itself,  thus  breaking-  up 
the  continuity  of  the  flow,  decreasing-  the  velocity,  and  tend- 
ing- to  the  formation  of  eddies  and  deposits. 

The  comparative  effect  of  the  two  styles  of  Y  branch 
upon-the  cross  section  of  the  stream  when  the  pipes  are  flow- 
ing- half  full  is  shown  in  Plate  I. 


CHAPTER  VIII. 

SPECIFICATIONS  AND  CONTRACT. 

Letting  the  Contract. — Having-  determined  upon  the 
plan  for  a  system  of  sewers,  the  sizes  of  the  pipes  required 
for  the  different  lines,  and  the  details  of  the  accessories,  the 
next  step  is  to  arrange  for  constructing  the  sewers. 

The  usual  way  is  to  advertise  for  bids  for  constructing" 
the  work  according"  to  the  plans  and  specifications  prepared 
by  the  Engineer.  A  description  of  the  work  and  approxi- 
mate quantities — subject  to  change  by  the  Eng'ineer — may  be 
given  either  in  the  notice  to  conti'actors,  or  in  an  estimate 
filed  with  the  detailed  plans  and  profiles,  which  have  been 
prepared  to  accompany  the  specifications.  All  drawings 
should  be  carefully  made  to  scale,  and  full  descriptions  of 
them  should  be  written  out,  so  that  every  point  may  be  made 
plain  and  nothing  left  to  be  inferred. 

As  a  guide  in  this  work  a  few  blank  forms  are  presented, 
which  can  be  modified  to  suit  the  requirements  of  particular 
cases. 

No  general  specifications  can  be  properly  applied  in 
work  where  the  conditions  are  unusual  and  these  specifica- 
tions are  to  be  used  onl}'  as  a  general  guide  upon  which  may 
be  founded  specifications  adapted  to  local  conditions  and 
local  laws. 


CHAP.  VIII.  SPECIFICATIONS    AND    CONTRACT.  139 

[form    for    ADVERTISEMENT.] 

NOTICE  TO  CONTRACTORS. 

Sealed  proposals  will  be  received  at  the  ofHce  of  the  Sewer  Commission 

in  the  City  of 

until . .  . .   o'clock ,  on  the day  of ,   i . . .    , 

for  constructing  sewers  in 

Forms  of  proposals,  copies  of  the  specifications  and  instructions  to  con- 
tractors may  be  obtained  of  the  Engineer;  and  the  plans  and  profiles  may  be 
seen  at  his  office. 

Each  bid  must  be  accompanied  by  a  deposit  of  S as  a  guarantee 

of  the  good  faith  of  the  bidder. 

The  Sewer  Commission  reserve  the  right  to  reject  any  or  all  bids. 

Address, 


Engineer. 
[instructions    to    CONTRACTORS.] 

TO  CONTRACTORS. 

1.  All  bids  must  be  made  upon  the  printed  forms,  to  be  obtained  at  the 
ofiice   of    the    Engineer,    and   enclosed    in    a  sealed   envelope,    directed  to  the 

Engineer  of  Sewers 

and  endorsed  upon  the  outside  of  the  envelope.   Proposal  for  constructing  Sew- 
ers in  the  City  of 

2.  Each  bid  must  be  accompanied  by  a  deposit   of Dollars, 

to  be  left  in  the  hands  of  the  City  Clerk,   subject  to  the  conditions  specified  in 
the  proposal  hereto  annexed,  as  a  guarantee  of  the  good  faith  of  the  bidder. 

3.  -Bids  shall  state  the  price  per  lineal  foot  of  pipes  of  each  size  laid  as 
herein  specified,  and  for  the  various  depths  of  trench  named,  also  for  all  other 
items  enumerated  in  the  schedule  opposite,  which  price  shall  be  in  full  for  all 
labor  and  materials  required  for  the  complete  execution  of  the  work. 

4.  All  prices  must  be  written  in  words,  and  also  stated  in  figures. 


140  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

5.  The  place  of  residence  of  each  bidder  must  be  given  after  his  signa- 
ture, which  must  be  written  in  full.  When  firms  bid,  the  individual  names  of 
the  members  shall  be  signed  in  full,  and  the  firm  name  added. 

6.  The  name  of  the  contractor  must  be  filled  in  the  blanks  left  for  that 
purpose. 

7.  The  City  of reserves  the  right 

to  reject  any  or  all  bids. 

8.  Bidders  are  requested  to  be  present  at  the  openmg  of  the  bids. 

g.     The  bond   required  of  the  successful   bidder  shall  be    in  the  sum   of 


[form  of  proposal.] 

PROPOSAL. 

To  the  Sc'Toer   Conuuissioii  of  the   Lily   of 

Gentlemen:  The  undersigned  hereby  propose  to  furnish  all  of  the- mate- 
rials and  do  all  of  the  work  required  to  complete  such  amount  of  the  above 
mentioned    work    as   shall    be    awarded    to    the    undersigned    by    the    City    of 

in  a  first   class  manner,   and  in  accordance  with 

the  specifications  hereto  annexed,  and  the  plans  and  drawings  of  the  same  on 
file  in  your  Engineer's  office,  at  the  following  prices,  viz.: 


CHAP.    VIII. 


SPECIFICATIONS    AND     CONTRACT. 


141 


ITEMS. 


Price  per  lineal  foot  for  furnishing  and  laying  i8-inch 
pipe,  including  Ys,  branches,  detachable  covers, 
and  cement  joints 


Price  per  lineal  foot  for  furnishing  and  laying  15-inch 
pipe,  including  Ys,  branches,  detachable  covers, 
and  cement  joints ^^ 


Price  per  lineal  foot  for  furnishing  and  laying  12-inch 
pipe,  including  Ys,  branches,  detachable  covers, 
and  cement  joints 


Price  per  lineal  foot  for  furnishing  and  laying  lo-inch 
pipe,  including  Ys,  branches,  detachable  covers, 
and  cement  joints 


Price  per  lineal  foot  for  furnishing  and  laying  8-inch 
pipe,  including  Ys,  branches,  detachable  covers, 
and  cement  joints 


Price  per  lineal  foot  for  furnishing  and  laying  6-inch 
pipe,  including  \'s,  branches,  detachable  covers, 
and  cement  joints 


Price  per  lineal  foot  for  all  excavation  and  back-filling 
under  6  feet  deep 


Price  per  lineal  foot  for  all  excavation  and  back-filling 
6  feet  or  over,  and  under  8  feet 


Price  per  lineal  foot  for  all  excavation  and  back-filling 
8  feet  or  over,  and  under  10  feet 


Price  per  lineal  foot  for  all  excavation  and  back-filling 
10  feet  or  over,  and  under  i2  feet 


Price  per  lineal  foot  for  all  excavation  and  back-filling 
12  feet  or  over,  and  under  14  feet 


Price  per  lineal  foot  for  all  excavation  and  back-filling 
14  feet  or  over,  and  under  16  feet 


Price  per  lineal  foot  for  all  excavation  and  back-filling 
16  feet  or  over,  and  under  18  feet 


Rock  Trench  per  lineal  foot,  per  foot  in  depth. 

Price  per  lineal  foot  for  repaving 

Man-holes,  complete,  each 

Lamp-holes,         "  "     

Flush-Tanks.       "  "     


Price  per  ton  for  iron  pipe,  laid  with  lead  joints,  com 
plete 


3-inch  drain  tile,  laid,  per  foot.. 

4-inch       " 

5-inch       "  "  " 


Price  in 
Figures. 


Price  in  Words. 


142  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 


6-inch  drain  tile,  laid  per  foot 

42-inch  brick  sewer,  laid,  per  foot.. 
40-inch  "  " 

36-inch  "  "  " 

30-inch  "  "  " 

24-inch  "  "  " 

fc Embankment,  price  per  cubic  jard. 


And hereby  agree  to  enter  into  a  contract  within  five  days  from  the 

date  of  your  acceptance  of  this  proposal,  to  finish  and  complete  said  work  (by 

the day  of, ),   according  to  the 

form  hereto  attached,  and  the  plans  and  specifications  on  file  in  the  office  of 
the  Engineer,  under  which  the  bid  was  made,  and  will  furnish  such  sureties  for 
the  faithful  performance  of  such  contract,  the  payment  for  materials  contracted 
for,  and  for  the  payment  of  laborer's  wages  and  liens  which  may  arise  there- 
from, as  shall  be  approved  by  the  Sewer  Commission. 

In  default  of  the  performance  of  any  of  the  conditions  on part  to 

be  performed,  the  sum  of Dollars,   which 

have  this  day  deposited  with  the  Sewer  Commission,  shall,  at  the  option  of  the 

said  Sewer  Commission,  be  absolutely  forfeited  to  the  City  of   

but  otherwise  said  sum  of Dollars 

shall  be  returned  to 

Dated  at the day  of 

I .  .  .  . 

[Contractors  Signature,] 


[P.   O.   Address,]      

No [State,] 

No 

City  Clerk. 


chap.  viii.  spkcificatioxs  and  contract.  143 

[fokm  for  specifications  and  contract,] 

ARTICLES  OF  AGREEMENT. 

Between  the  City  of 

party  of  the  first  part,   and 

Contractor,  party  of  the  second  part,  for  building 

Sewers  in ' 


This  Agreement,   made  and  entered  into  this day  of 

in  the  year  one  thousand   hundred 

, b\-  and  between  the  City  of 

party  of  the  first  part,  and 

Contractor. .,  party  of  the  second  part. 

Witnesscth,  Whereas,  The  City  of    in  the 

State  of : by  virtue  of  the  authority  vested  in  the 

Sewer  Commission  by  the  Legislature  of  the  State  of 

and    by    the    Charter  and    Ordinances  of  the  City,  agree  to  let  unto  the  said 

Contractor .  .    the  work  of 

constructing  certain Sewers,   as  per  plans  and  profiles 

of  the  work  on  file  in  the  office  of  the  Engineer  of  Sewers. 

Now,  Therefore,  in  consideration  of  the  payments  and  covenants  herein- 
after mentioned  to  be  made  and  performed  by  said  party  of  the  first  part,  the 

said hereby  covenants  and  agrees  to  do  the 

work  above  mentioned  in  a  substantial  and  workmanlike  manner,  in  conformity 
with  the  plans,  profiles  and  specifications  of  such  work  on  file  in  the  office  of 
the  Engineer,  in  strict  obedience  to  the  directions  which  may  from  time  to 
time  be  given  by  the  said  Engineer  or  his  duly  authorized  assistants,  and  in 
accordance  with  the  following  specifications. 

SPECIFICATIONS  FOR  SEWERS. 

In  the  City  of 

BRICK    SEWERS. 

I.  The  ground  shall  be  excavated  in  open  trenches  to  the  necessary  width 
and  depth.  The  trenches  shall  be  opened  at  least  one  foot  wider  on  each  side 
than  the  exterior  diameter  of  the  sewer  intended  to  be  laid.  The  bottom  of 
the  trenches  shall  be  formed  to  the  required  grade  and  to  the  shape  of  the 
sewer,  so  that  the  whole  surface  of  the  under  half  of  the  sewer  shall  have  an 


144  THE   SEPARATE   SYSTEM    OF    SEWERAGE. 

even  bearing  throughout.  In  the  trench  thus  formed  shall  be  spread  cement 
mortar,  as  the  bricks  are  laid,  not  less  than  one  inch  thick;  upon  this  shall  be 
laid  the  inverted  arch.  The  upper  half  of  the  sewer  shall  be  covered  with  a 
coating  of  cement  mortar  not  less  than  %  inch  thick.  The  work  shall  be 
backed  in,  carefully  ramming  and  packing  under  and  around  the  sewer  with 
proper  tools,  by  a  trusty  person  approved  by  the  Engineer. 

2.  In  the  construction  of  the  work,  none  but  the  best  quality  of  whole 
brick,  burnt  hard  entirely  through,  shall  be  used.  They  shall  be  thoroughly 
wet  immediately  before  being  laid.  Every  brick  is  required  to  have  full 
cement  joints  on  the  bed,  sides  and  ends,  unless  otherwise  ordered  by  the 
Engineer,  which  for  each  brick  is  to  be  formed  at  one  operation,  and  in  no 
case  is  to  be  made  by  working  in  the  cement  after  the  brick  is  laid;  not  more 
than  two  courses  of  bricks  shall  be  laid  without  being  lined.  The  bricks  in 
each  course  shall  be  laid  as  stretchers  and  shall  break  joints  with  those  of 
adjoining  courses.  The  bricks  shall  be  culled  before  being  brought  upon  the 
ground,  and  all  brick  of  an  improper  quality,  and  all  bats,  removed  from  the 
street. 

3.  The  cement   mortar  shall  be  composed   of  the  best   quality  of  fresh 

ground cement,   mixed  in  the  proper  proportion  of  one  part  of 

cement  to  two  parts  of  clean  sharp  sand,  free  from  loam  and  shall  be  used 
immediately  after  it  has  been  mixed;  any  that  has  stiffened  by  commencing  to 
set  shall  be  rejected.  All  cement  will  be  subject  to  inspection  and  test  before  it 
is  used,  the  Engineer  to  decide  upon  the  character  and  severity  of  the  test,  and 
if  found  of  improper  quality  it  must  be  immediately  removed  from  the  work. 

4.  Whenever  it  shall  be  deemed  necessary  by  the  Engineer,  the  sewer 
shall  be  built  in  a  wooden  invert  constructed  of  ij^  inch  pine  plank,  securely 
nailed  to  2x3^  inch  ribs  placed  not  more  than  six  feet  apart  and  formed  to  cor- 
respond with  the  exterior  of  the  sewer,  which  invert  shall  extend  each  side  of 
the  sewer  at  least  one-third  the  height  of  the  same. 

5.  The  sewer  shall  conform  in  shape  and  size  to  the  pattern  furnished  by 
the  contractor,  and  made  from  drawings  furnished  by  the  engineer. 

6.  The  whole  of  the  joints  of  the  inner  face  of  the  sewer,  below  the 
springing  line  of  the  arch,  to  be  smoothly  and  properly  struck.  Those  above 
the  springing  line,  scraped  even  with  the  bricks,  as  soon  as  the  centres  are 
struck.     The  refuse  mortar  must  be  immediately  removed  from  the  sewer. 

7.  In  keying  the  crown  of  the  arch  no  headers  are  to  be  used.  The  inner 
and  outer  courses  of  stretchers  are  to  be  carried  over  and  keyed  separately,  and 
each  course  in  the  crown  of  the  arch  is  to  be  thoroughly  grouted  with  grout 
composed  of  equal  parts  of  clean,  sharp  sand,  and  best  quality  of  fresh  ground 
cement    as  directed  by  the  Engineer. 


CHAP.   VIII.  SPIOCIFICATIONS    AND    CONTRACT.  145 

8.  All  brick  work  must  be  racked  back  in  courses,  and  when  new  work  is 
to  be  joined  to  it,  the  surface  of  the  bricks  must  be  cleaned  and  moistened. 
The  inner  ring  shall  be  laid  of  selected  brick.  No  inside  joint  shall  be  greater 
than  3-16  inch. 

9.  The  upper  arch  shall  be  laid  upon  centres,  not  less  than  10  feet  long 
for  straight  work.  For  curved  brick  sewers,  the  centres  must  correspond  with 
the  radius  of  the  curve.  The  centres  shall  not  be  drawn  until  the  back  filling 
is  above  the  top  of  the  arch,  without  the  permission  of  the  Engineer.  All 
centres  and  templets  shall  be  scraped  clean  before  use. 

The  contractor  will  be  held  responsible  for  any  distortion  of  the  sewer  by 
reason  of  the  subsequent  settlement  of  the  trenches. 

10.  Man-holes  shall  be  built  into  the  sewer  at  such  places  as  the  Engineer 
may  direct;  the  side  walls  to  begin  at  the  springing  line  of  the  upper  arch  of 
the  sewer.  Size,  form,  thickness  of  wall,  cover  and  all  details  to  conform  to 
the  Engineer's  drawings  accompanying  the  specifications.  Wrought  iron  steps 
of  7-8  inch  round  iron  shall  be  placed  in  the  man-holes.  Distance  apart  of 
steps,  18  inches;  length  of  tread,  10  inches;  projection  from  brick  work,  4 
inches.  The  iron  to  extend  through  the  wall  and  clinch  one  inch  on  the  out- 
side. 

11.  Branch  sewer  connections  and  house  connections  shall  be  built  into 
the  sewer  at  such  points  and  in  such  manner  as  the  Engineer  may  direct. 
Branches  not  to  exceed  on  an  average,  one  every  25  feet  on  each  side. 

EARTHENWARE    PIPE    SEWERS. 

12.  The  sewers  shall  be  constructed  of  first  quality  vitrified,  salt-glazed 
sewer  pipe,  sound  and  well  burned  thrcughout  their  thickness,  impervious  to 
moisture,  of  smooth  and  well  glazed  exterior  and  interior  surfaces,  free  from 
cracks,  flaws,  blisters,  fire-checks,  end  all  other  imperfections,  circular  in  the 
bore,  of  true  form  in  their  lengths,  whether  straight  or  curved,  internally  of 
the  exact  specified  diameter,  r  nd  of  uniform  standard  thickness. 

13.  All  pipe  shall  be  socket  pipe,  with  true  and  circular  sockets  concen- 
tric with  the  bore  of  the  pipe,  and  shall  be  furnished  in  pieces  two  feet  long. 
For  all  junction  pieces,  a  well  fitted  vitrified  stopper  shall  be  furnished,  with- 
out charge. 

14.  A  Y  branch  connection  of inches,  in  diameter  shall  be  provided 

every  twenty-five  feet  en  each  side,  when  ordered  by  the  Engineer. 

IRON   PIPE. 

15.  Iron  pipe  shall  be  used  where  the  sewer  runs  under  or  through  water- 
ways— either  natural  or  artificial — or  under  a  railroad,  or  wherever  it  is  deemed 
necessary  by  the  Engineer.     The  joints  shall  be  of  lead  properly  caulked.     The 


146  THE    SEPARATE    SYSTE:M    OF    SEWERAGE. 

lengths  of  pipe,  their  diameter  and  thickness  to  be  as  directed  by  the  Engineer. 
The  weight  of  each  pipe  shall  be  plainly  marked  on  it  before  leaving  the 
factory. 

i6.  The  iron  pipe  shall  be  paid  for  by  the  ton,  laid  in  place  with  joints 
complete. 

LOCATION. 

17.  The  sewers  shall  be  located  on  the  lines  shown  on  the  plans  of  the 
work,  and  will  be  staked  out  by  the  Engineer.  This  line,  whenever  practica- 
ble, will  be  on  the  centre  line  of  the  street.  The  Commissioners,  however, 
reserve  the  right  to  move  the  line  of  sewers  to  the  right  or  left  whenever 
obstructions  are  met  which  render  a  change  of  line  desirable. 

18.  The  contractor  will  be  required  to  preserve  all  stakes  and  bench 
marks  until  permission  is  given  by  the  Engineer  to  remove  them. 

ig.  The  line  for  trenches  will  be  indicated  by  stakes  set  at  one  side  of  the 
trench.  A  width  of  at  least  two  feet,  on  the  side  of  the  trench  where  the  stakes 
are,  shall,  as  the  work  progresses  be  kept  free  from  obstruction. 

EXCAVATION'. 

20.  All  excavations  shall  be  by  open  cut  from  the  surface.  No  tunneling 
will  be  allowed,  except  written  permission  be  previously  obtained  from  the 
Engineer. 

21.  The  contractor  will  be  required  to  keep  the  sides  of  the  excavation 
vertical,  by  bracing  or  otherwise;  but  no  allowance  will  be  made  therefor 
unless  the  same  is  left  in  the  trench  by  written  order  of  the  Engineer. 

22.  The  excavation,  at  the  bottom,  is  to  be  made  and  shaped  as  nearly  as 
possible  to  fit  the  lower  half  of  the  pipe  to  be  laid,  with  holes  cut  at  the  joints 
for  the  sockets  to  rest  in,  so  that  the  pipe  shall  have  a  uniform  bearing  on  the 
ground  from  end  to  end. 

23.  At  the  height  of  half  of  the  diameter  of  the  pipe  from  the  bottom, 
that  is,  at  the  height  of  the  greatest  horizontal  diameter  of  the  pipe,  all 
trenches  are  to  be  eighteen  inches  wider  than  the  greatest  diameter  of  the  pipe 
to  be  laid  therein. 

24.  The  trench  shall  be  dug  to  within  six  inches  of  grade  by  measurement 
from  the  witness  stakes  on  the  surface.  The  last  six  inches  shall  be  taken  out 
after  the  grade  pegs  have  been  set  in  the  bottom  of  the  trench  by  the  contractor 
under  the  direction  of  the  Engineer. 

25.  The  excavations  for  all  man-holes,  flush  tanks,  and  other  accessories 
shall  be  sufficient  to  leave  at  least  one  foot  in  the  clear  between  their  outer 
surfaces  and  the  embankment  or  timber  which  may  be  used  to  protect  it. 


CHAP,   \-iri.  SPKCIl'ICATIOXS    AND    CONTKAC'l".  1-17 

26.  The  approximate  depth  of  the  cutting  will  be  given  by  the  Engineer 
before  the  excavation  is  begun.  Grade  and  line  will  be  given  by  the  Engineer 
every  25  feet  at  the  bottom  of  the  trench,  on  stakes  to  be  furnished  and  set  by 
the  contractor;  or  on  overhead  pieces,  from  which  the  position  of  the  invert 
may  be  determined  by  a  line  parallel  therewith. 

27.  In  no  case,  without  previous  written  permission  from  the  Engineer, 
shall  more  than  500  feet  of  trench  be  opened  in  advance  of  the  completed 
sewer  and  on  the  completion  of  each  500  feet  of  sewer,  the  street  surface  must 
be  restored  in  good  condition  and  all  surplus  material  and  rubbish  from  that 
section  be  immediately  removed. 

28.  The  material  excavated  shall  be  laid  compactly  on  the  sides  of  the 
trench  and  kept  trimmed  up  so  as  to  be  of  as  little  inconvenience  as  possible  to 
the  traveling  public  and  adjoining  tenants. 

29.  The  contractor  shall  not  obstruct  the  gutter  of  any  street,  but  shall 
use  all  proper  measures  to  provide  for  the  free  passage  of  surface  water  along 
the  gutters. 

30.  The  contractor  shall  provide  for  all  water  courses  and  drains  inter- 
rupted during  the  progress  of  the  work,  and  replace  them  in  as  good  condition 
as  he  found  them.  The  use  of  any  portion  of  the  sewers  shall  not  be  con- 
structed as  an  acceptance  of  them  by  the  Commissioners. 

31.  No  additional  compensation  shall  be  allowed  for  excavating  man- 
holes, or  flush  tanks  over  the  price  per  lineal  foot  for  trench. 

32.  The  contractor  shall  keep  the  trenches  free  from  water  during  the 
progress  of  the  work,  as  no  pipe  of  masonry  shall  be  laid  in  the  water. 

PROTECTION    OF    PROPERTY. 

33.  The  contractor  shall  at  his  own  expense,  shore  up,  protect,  and  make 
good,  as  may  be  necessary,  all  buildings,  walls,  fences  or  other  property 
injured,  or  liable  to  be  injured  during  the  progress  of  the  work;  and  the  con- 
tractor will  be  held  responsible  for  all  damage  which  may  happen  to  neighbor- 
ing property  from  neglect  of  this  precaution,  or  from  any  other  cause  connected 
with  the  prosecution  of  the  work. 

PROTECTION    OF    WATER    AND    GAS    PIPES,    ETC. 

34.  The  contractor  shall  do  whatever  may  be  necessary  to  keep  in  posi- 
tion and  to  protect  from  injury  all  water  and  gas  pipes,  lamp  posts,  service 
pipes,  and  all  other  fixtures  which  may  be  met  with  in  carrying  on  the  work. 

35.  In  case  any  of  the  said  gas  or  water  pipes  or  other  fixtures  be  dam- 
aged, they  may  be  repaired  by  the  parties  having  control  of  the  same,  and  the 
expense  of  such  repairs  shall  be  deducted  from  the  amounts  which  may  become 
due  the  contractor. 


148  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

PROTECTION    AGAINST    ACCIDENTS. 

36.  The  contractor  shall  erect  suitable  barriers  around  all  excavations,  to 
prevent  accidents  to  passengers  on  the  streets,  and  shall  place  and  maintain 
during  the  night  sufficient  red  lights  on  or  near  the  work. 

37.  The  contractor  shall  have  charge  of,  and  be  responsible  for,  the 
entire  line  of  sewers  for  whose  construction  he  has  contracted,  until  their 
completion  and  acceptance.  He  shall  also  be  liable  for  any  defects  which  may 
appear  in  his  work  before  the  final  payments  specified  herein. 

BACK-FILLING. 

38.  The  earth  filled  around  and  on  top  of  the  sewers  shall  be  free  from 
stones,  and  tamped  with  the  utmost  care,  so  as  to  obtain  the  greatest  compact- 
ness and  solidity  possible.  In  filling,  the  earth  shall  be  kept  at  the  same  height 
on  both  sides  of  the  sewer  when  required  by  the  Engineer.  The  earth  shall  be 
rammed  in  layers  of  not  more  than  one  foot  thick  up  to  the  surface  of  the 
street,  and  in  no  case  shall  the  number  of  men  filling  be  more  than  twice  the 
number  of  men  ramming.  In  lieu  of  ramming,  the  earth  may  be  thoroughly 
puddled. 

39.  The  contractor  is  required  not  to  sell,  remove  or  permit  to  be 
removed  from  the  line  of  the  work,  before  the  trench  shall  have  been  refilled, 
any  sand,  gravel,  or  earth  excavated  therefrom  which  may  be  suitable  and 
required  for  refilling. 

40.  The  trench  must  in  all  cases  be  filled  to  the  proper  grade  with  suit- 
able material.  Should  there  be  a  deficiency  of  proper  material  for  refilling  the 
trench  the  contractor  will  be  required  to  furnish  the  same  at  his  own  cost. 

REPAYING    AND    RESTORING    STREETS. 

41.  When  the  pavement  has  been  removed,  it  must  be  replaced  by  the 
contractor  and  left  in  as  good  condition  as  it  was  before  being  removed. 

42.  As  the  trenches  are  filled  in  and  the  work  completed,  the  contractor 
shall  remove  all  surplus  material,  without  additional  compensation,  to  localities 
not  interfering  with  the  regulations  of  the  city,  and  shall  leave  all  roads  and 
places  free,  clean  and  in  good  order. 

43.  All  work  of  restoring  the  surface  of  the  streets  shall  be  done  to  the 
satisfaction  of  the  superintendent  of  streets. 

44.  If  at  any  time  during  a  period  of  one  year  from  the  date  of  the  final 
completion  and  acceptance  of  the  sewer,  the  roadway  on  the  line  of  the  sewer 
shall  require  regrading,  repaving  or  regraveling,  by  reason  of  the  settlement  of 
the  trenches,  the  Commissioners  shall  notify  the  party  of  the  second  part  to 
make  the  repairs  so  required;  and  if  the  party  of  the  second  part  shall  neglect 
for  a  period  of  ten  days  to  make  such  repairs  to  the  satisfaction  of  the  Com- 


CHAP.  VIII.  spi:cii'iCA  rioxs  and  contract.  141> 

missioners,  then  the  Commissioners  shall  have  the  right  to  cause  the  repairs  to 
be  made,  and  to  pay  the  expense  thereof  out  of  the  sum  retained  for  that 
purpose. 

EMBANKMENT. 

45.  Where  embankment  is  necessary  to  support  the  foundations  of  the 
sewer,  or  to  cover  or  protect  it  in  any  way,  it  shall  be  made  of  the  width  and 
slopes  as  shown  on  the  plan.  Th.e  surface  of  the  ground  receiving  the  embank- 
ment shall  be  carefully  cleared  of  all  muck  or  unsuitable  material,  of  whatever 
nature 

The  embankment  shall  then  be  formed  of  good  loam  or  gravel,  free  from 
all  stones  over  four  inches  in  diameter,  and  of  those  below  that  size  in  a  pro- 
portion not  exceeding  one  part  of  stone  to  three  parts  of  earth  in  any  place. 

If  built  to  support  the  foundation  of  the  sewer,  the  material  is  to  be  depos- 
ited in  layers  of  not  more  than  six  inches  in  thickness,  each  layer  to  be  sepa- 
rately compacted  by  heavy  iron  rollers,  or,  where  these  cannot  be  used,  by 
heavy  paver's  rammers.  No  breaks,  steps  or  irregularities  in  the  distribution 
of  material  or  formation  of  the  layers  will  be  allowed,  and  the  whole  embank- 
ment is  to  be  carried  up  evenly  so  as  to  make  a  compact  and  solid  foundation. 

PIPES  — HOW    L.AID. 

46.  All  pipes  over  eight  inches  in  diameter  shall  be  laid  with  a  straight 
edge.  One  end  of  the  straight  edge  shall  be  placed  on  the  nearest  grade  peg 
and  the  other  on  the  flow  line  of  the  pipe  already  laid,  and  the  pipe  shall  be  so 
adjusted  as  to  be  in  contact  with  the  straight  edge  throughout  its  length. 

All  pipes  eight  inches  and  less  in  diameter,  except  house  branches,  shall  be 
laid  in  the  following  manner:  A  mason's  line  shall  be  tightly  stretched  parallel 
to  the  grade  and  slightly  above  the  sockets  of  the  pipes.  This  line  shall  be 
supported  over  the  centre  at  distances  not  greater  than  twenty-five  feet  apart. 
The  exact  grade  for  each  pipe  shall  be  obtained  by  measuring  down  from  this 
line  to  the  invert  of  the  sewer. 

47.  Especial  care  must  be  taken  to  lay  the  pipe  to  the  exact  grade  and 
line. 

48  All  pipes,  previous  to  being  lowered  into  the  trench,  shall  be  fitted 
together  and  matched,  so  that  when  joined  in  the  trench  they  may  form  a  true 
and  smooth  line  of  pipes.  No  pipes  shall  be  trimmed  in  any  case.  Pipes 
which  do  not  fit  truly  shall  be  rejected. 

JOINTS. 

49.  A  gasket  of  oakum  or  other  material  approved  by  the  Engineer  shall 
be  pressed  into  the  joint  around  the  entire  circumference  of  the  pipe  to  pre- 


150  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

vent  the  entrance  of  cement  to  the   inside   of  the  pipe.      No  joint    shall    be 
cemented  until  the  gasket  of  the  next  joint  in  advance  has  been  completed. 

50.  The  cement  shall  be  pressed  into  the  space  between  the  socket  and 
spigot  so  as  to  entirely  fill  the  space,  and  the  bevel  joint  at  the  end  of  the 
socket  shall  be  smoothly  and  evenly  made.  Special  care  must  be  taken  to 
make  perfect  joints  at  the  bottom  of  the  pipe. 

51.  The  excavation  made  for  the  socket  of  the  pipe  shall  be  filled  with 
sand  to  support  the  cement  firmly  in  position. 

When  the  joint  is  completed  great  care  must  be  taken  not  to  disturb  the 
pipes. 


52.  The  cement  for  filling  the  joints  shall  be  pure  fresh  ground 

cement,  of  best  quality,   with  only  enough   water  added  to  give  it  the   proper 
consistency,  and  shall  be  mixed  only  as  needed  for  use. 

BRANCHES,     "t's,  "    ETC. 

53.  The  "Y"  branches,  "T's,"  lamp-holes,  hand-holes,  and  man-holes 
shall  be  placed  at  points  indicated  by  the  Engineer.  They  shall  not  be  covered 
until  he  has  noted  and  recorded  their  exact  position.  The  "Y"  branches  shall 
be  elevated  to  correspond  to  the  lateral  sewers  and  house  drains  entering  them. 
They  shall  be  closed  with  an  earthenware  cap,  and  the  space  above  the  cap 
shall  be  filled  with  sand,  covered  with  a  thin  coating  of  cement. 

SPECIAL    PIECES. 

54.  Special  pieces,  such  as  Y  branches,  curves,  T's,  etc  ,  shall  be  made 
according  to  drawings  furnished  by  the  Engineer. 

SEWERS    TO    BE    KEPT    CLEAN    AND    FREE    FROM    WATER. 

55.  All  the  pipes  must  be  kept  thoroughly  clean,  and  no  water  will  be 
allowed  to  flow  through  them,  during  the  construction  of  the  sewers. 

56.  When  the  trench  is  left  for  the  night,  or  the  pipe-laying  is  stopped  by 
rain  storms  or  any  other  cause,  the  ends  of  the  pipes  must  be  closed  water-tight 
with  bricks  and  cement 

57.  When  running  quicksand  or  other  treacherous  ground  is  encountered, 
the  work  shall  be  carried  on  day  and  night,  should  the  Engineer  so  require. 

ARTIFICIAL    FOUNDATION. 

58.  Whenever  ordered  by  the  Engineer,  in  writing,  the  contractor  shall 
excavate  to  such  depth  below  grade  as  the  Engineer  may  direct,  and  the  exca- 
vation shall  be  brought  to  grade  with  such  material  as  shall  be  ordered  by  the 
Engineer;   the  extra  work  to  be  paid  for  upon  the  estimate  of  the  Engineer. 


CHAP.   VIII.  SPIXIIICATIOXS    AND    CONTKACT.  151 

59.  If  the  contractor  excavates  below  grade  without  orders,  he  will  be 
required,  at  his  own  expense,  to  fill  the  excess  of  excavation  with  such  material 
as  the  Engineer  may  direct. 

60.  Concrete  foundations  shall  be  placed  under  the  flush-tanks  and  man- 
holes. 

ROCK    CUT. 

61.  When  blasting  is  resorted  to  for  making  the  excavations,  the  trench 
shall  be  covered  carefully  on  the  top  and  sides  with  heavy  timbers  and  plank, 
to  prevent  fragments  of  rock  from  being  thrown  out. 

In  rock  cut,  the  rock  shall  be  taken  out  of  the  trench  to  a  depth  of  four 
inches  below  the  bell  of  the  pipe  when  laid.  The  refilling  from  the  bottom  of 
the  trench  to  one  foot  above  the  bell  of  pipe  shall  be  of  earth,  free  from  stones, 
or  such  material  as  shall  be  approved  by  the  Engineer. 

62.  All  damages  or  injury  to  persons  or  property  resulting  from  blasting 
operations,  or  from  neglect  in  properly  guarding  the  trenches,  must  be  paid  by 
the  contractor;  and  no  compensation  to  said  contractor  for  losses  thus  incurred 
will  be  allowed. 

LAMP-HOLES. 

63.  Lamp-holes  shall  be  constructed  by  placing  an  eight-inch  "T"  branch 
vertically  in  the  sewer,  and  bringing  it  up  to  within  one  foot  of  the  street  sur- 
face by  adding  pipes  of  the  same  diameter.  The  top  of  the  lamp-hole  shall  be 
protected  by  cover,  as  shown  in  the  detail  drawing. 

MAN-HOLES. 

64.  The  man-holes  shall  be  constructed  of  hard  brick,  laid  in  cement 
mortar,  and  plastered  outside  with  cement  mortar  and  washed  inside  with  pure 
cement.  The  thickness  of  the  wall  shall  be  eight  inches.  The  form  shall  be 
a  truncated  cone  (see  drawings).  The  bottom  shall  be  formed  of  concrete,  and 
the  top' of  the  concrete  shall  be  on  a  level  with  the  bottom  of  the  sewer  pipe, 
and  the  top  of  the  cover  on  a  level  with  the  street  surface.  Particular  care 
must  be  taken  in  forming  the  bottom  of  man-holes  to  make  the  curves  of  tribu- 
tary sewers  as  easy  as  possible.  The  top  shall  be  covered  with  a  perforated 
cast  iron  cover,  with  dust  pan  underneath.     (See  drawings.) 

FLUSH    TANKS. 

65.  Flush-tanks  shall  be  constructed  of  hard-burned  bricks,  carefully  laid 
in  cement  mortar,  so  as  to  be  water  tight.  They  shall  be  plastered  outside  and 
inside  with  cement  mortar.     (For  form,  size  and  details  see  drawings.) 

66.  The  emptying  device  for  the  flush  tanks  shall  be  selected  and  pur- 
chased by  the  Commissioners  and  shall  be  properly  set  by  the  contractor. 


152  thp:  separate  system  of  sewerage. 

67.  The  water  supply  pipe,  within  the  flush  tank,  and  extending  through 
the  wall  and  one  foot  outside  of  the  wall,  together  with  a  suitable  brass  stop- 
cock for  regulating  the  water  supply,  shall  be  furnished  by  the  contractor. 

BRICK    MASONRY. 

68.  None  but  the  best  quality  of  whole,  sound,  well  shaped  brick,  burned 
hard  entirely  through,  shall  be  used.  They  are  to  be  culled  when  delivered 
upon  the  ground,  and  all  bats  and  imperfect  bricks  are  to  be  immediately 
removed  from  the  work. 

All  bricks  are  to  be  thoroughly  wet  immediately  before  laying.  Every 
brick  is  required  to  be  laid  in  a  full  and  close  joint  of  cement  mortar,  on  its 
beds,  ends,  and  sides,  at  one  operation.  In  no  case  is  mortar  to  be  slushed  in 
afterwards. 

CEMENT    MORT-AR. 

6g.     All  cement  mortar  for  man-holes,   lamp-holes  and   concrete,  shall  be 

made  of  best  quality  of  fresh  ground cement  and  clean  sharp  sand, 

in  the  proportion  of  one  measure  of  cement  to  two  of  sand.  The  sand  and 
cement  shall  be  thoroughly  mixed  dry,  and  such  quantity  of  water  added  as  to 
form  a  paste  of  the  proper  consistency.  All  mortar  shall  be  fresh  for  the  work 
in  hand.  No  mortar  that  has  begun  to  set  shall  be  used.  Every  facility  for 
inspecting  and  testing  the  cement  shall  be  furnished  by  the  contractor. 

CONCRETE. 

70  The  concrete  used  on  the  work  shall  be  made  of  three  parts  of  cement 
mortar  (made  as  described)  and  two  parts  of  clean  gravel,  or  broken  stone.  It 
shall  be  quickly  and  thoroughly  mixed,  and  iramjdiately  deposited  in  place. 

MATERIALS. 

71.  All  materials  shall  be  furnished  by  the  contractor,  and  shall  be  sub- 
ject to  inspection  and  acceptance  by  the  Engineer. 

LENGTH    OF    SEWER. 

72.  The  length  of  the  sewer  will  be  measured  on  the  centre  line  of  the 
completed  sewer. 

INTERPRETATION    OF    TERMS. 

73.  Wherever  the  word  "Commissioners"  is  used  in  these  specifications, 
it  shall  be  held  to  mean   the  Board  of  Sewer   Commissioners   of  the  City   of 


Wherever  the  word  "Engineer"  is  used,  it  shall  be  held  to  mean  the  Engi- 
neer in  charge  of  the  sewers,  or  his  authorized  assistant. 


CHAP.    VIII.  SPKCIFICATIONS    AND     CONTKAC'J'.  1.53 

Wherever  the  word  "Contractor"  is  used,  it  shall  be  held  to  mean  either 
any  contractor  or  firm  of  contractors,  or  any  member  of  a  firm,  contracting  for 
work  herein  specified. 

GENERAL    STIPULATIONS. 

74.  The  contractor  shall  start  the  work  at  such  points  on  the  line  of  the 
sewer  as  the  Engineer  may  from  time  to  time  direct,  and  shall  progress  from 
the  outlet,  or  towards  the  outlet,  at  the  option  of  the  Engineer. 

75.  Xo  pipes  or  ma.sonry  shall  be  laid  in  freezing  weather. 

76.  None  of  the  work  shall  be  sub-let  without  the  permission  of  the  Com- 
missioners. 

77>  The  contractor  shall  also  do  such  extra  work  in  connection  with  his 
contract  as  the  Engineer  may  in  writing  specially  direct,  and  in  a  first-class 
manner,  but  no  claim  for  extra  work  shall  be  allowed  unless  the  same  was  done 
in  pursuance  of  a  written  order,  as  aforesaid,  to  do  the  work  as  such  and  the 
claim  presented  at  the  first  estimate  after  the  work  was  done.  Extra  work 
shall  be  paid  for  on  a  basis  of  15  per  cent,  in  advance  of  the  actual  cost  of 
labor  and  material  as  determined  by  the  Engineer. 

78.  Although  the  Engineer  may  assent  to  special  means  for  prosecuting 
work  in  difficult  cases,  this  will  not  relieve  the  contractor  of  the  responsibility 
as  to  the  result. 

79.  The  contractor  upon  being  so  directed  by  the  Engineer,  shall  remove, 
or  rebuild,  or  make  good,  at  his  own  cost,  any  work  which  the  latter  shall 
decide  to  be  deficiently  executed. 

So.  No  work  shall  be  covered  until  it  has  been  examined  by  the  Engineer 
or  inspector. 

81.  The  Contractor  will  be  required  to  observe  all  City  Ordinances  in 
relation  to  obstructing  streets,  keeping  open  passage  ways  and  protecting  the 
same  where  exposed,  and,  generally,  to  obey  all  Ordinances,  Rules  and  Regu- 
lations controlling  or  limiting  those  engaged  on  the  work. 

82.  At  the  suspension  of  any  work  the  trenches  shall  be  filled  and  the 
street  left  clean  and  free  for  travel. 

83.  The  contractor  shall  give  notice  in  writing,  at  least  twenty-four  hours 
before  breaking  ground,  to  all  persons  (Superintendents,  Inspectors  or  other- 
wise) in  charge  of  property,  streets,  gas  pipes,  water  pipes,  railroads  or  other- 
wise, that  may  be  effected  by  his  operations.  And  it  is  further  agreed  that  the 
said  part of  the  second  part  shall  not  cause  any  hindrance  to  or  inter- 
ference with  any  such  company  or  companies  in  protecting  their  said  work;  but 
that  the  said  part of  the  second  part  will  suffer  the  said  company  or  com- 
panies to  take  all  such  measures  as  they  may  deem  necessary  for  the  purpose 
aforesaid. 


154  THE  skparatp:  system  of  sewerage:. 

84.  The  Commissioners  shall  have  a  right  to  make  alterations  in  the  line, 
grade,  plan,  form  or  quantity  of  the  work  herein  contemplated,  either  before 
or  after  the  commencement  of  the  work.  If  such  alterations  diminish  the 
quantity  of  work  to  be  done  they  shall  not  constitute  a  claim  for  damages,  or 
for  anticipated  profits  on  the  work  dispensed  with;  if  they  increase  the  amount 
of  work,  such  increase  shall  be  paid  for  according  to  the  quantity  actually  done, 
and  the  price  or  prices  stipulated  for  such  work  in  this  contract. 

85.  If  any  person  employed  by  the  contractor  on  the  work  shall  appear  to 
the  Engineer  to  be  incompetent  or  disorderly,  he  shall,  on  the  requisition  of 
the  Engineer,  be  immediately  discharged,  and  such  person  shall  not  be  again 
employed  upon  the  work  without  the  permission  of  the  Engineer. 

86.  The  work  embraced  in  this  contract  shall  be  begun  within days 

after  the  award  of  this  contract,  and  carried  on   regularly  and  uninterruptedly 

thereafter,  with  such  a  force  as  to  secure  its  full  completion  by 

;  but  should  the  work  be  delayed  or  interrupted  by   the   City,    after  the 

service  of  such  notice,  the  contractor  shall  be  entitled  to  an  extension  of  time 
equal  to  the  time  of  such  interruption  or  delay,  which  shall  be  determined  by 
the  Engineer;  the  time  of  beginning,  rate  of  progress,  and  time  of  completion 
being  essential  conditions  of  this  contract;    and  if   the  contractor   shall   fail   to 

complete  the  work  by  the  time  above  specified,  the  sum  of per  day, 

for  each  and  every  day  thereafter,  until  such  completion,  shall  be  deducted 
from  the  moneys  payable  under  this  contract.  This  sum  shall  be  in  addition  to 
any  penalties  otherwise  specified. 

87.  No  charge  shall  be  made  by  the  contractor  for  hindrances  or  delay 
from  any  cause  during  the  progress  of  any  portion  of  the  work  embraced  in 
this  contract 

88.  No  variation  from  the  regular  prices  named  in  the  proposal  will  be 
made  or  allowed,  whether  the  material  through  which  the  trenches  are  e.xca- 
vated  is  hard  or  soft,  or  whether  it  is  composed  of  rock,  boulders,  walls  or  com- 
mon earth.  The  Board  of  City  Commissioners  will  not  consider  themselves 
bound  to  notify  or  inform  contractors  where  material  that  is  hard  or  e.xpensive 
to  excavate  occurs,  or  will  be  liable  to  be  encountered.  Furthermore  no  com- 
pensation for  trenching  done  in  excess  of  the  orders  of  the  Engineer  will  be 
allowed. 

89.  A  watchman  shall  be  employed  on  the  work  at  night  whenever  in  the 
opinion  of  the  Engineer  it  shall  be  necessary. 

90.  House  branches  shall  be  laid  to  a  point  just  within  the  curb  lines 
where  the  Engineer  shall  direct. 

91.  Should  any  dispute  arise  between  the  Engineer  and  contractor  as  to 
the  true  meaning  of  the  drawings  or  specifications  in  any  point,  or  as  to   the 


CHAP.    VIII.  SPKCIFICATIONS    AND    CONTRACT.  155 

manner  of  the  execution  of  the  work,  or  the  quality  of  the  work  executed,  the 
decision  of  the  former  shall  be  final  and  concjusive. 

92.      And  the  said 

contractor,  hereby  expressly  binds  himself  to  indemnify  and  save  harmless  the 

City  of from  all  suits  or  actions  of  every  name  and  description 

brought  against  the  said  City,  for,   or  on  account  of  any  injuries  or  damages 

received  or  sustained  by  any  party  or  parties  by  or  from  the  said 

or  his 

servants  or  agents,  in  the  construction  of  said  work,  or  by  or  in  consequence  of 
any  negligence  in  guarding  the  same,   or  any  improper  materials  used   in  its 

construction,  or  by  or  on  account  of  any  act  or  omission  of  the  said 

or  his  agents. 

93.  Said  part. . .  .of  the  second  part  further  agree,  .that  in  case  of  failure  to 
furnish  materials  or  execute  the  work  in  accordance  with  the  plans  and  specifi- 
cations to  the  satisfaction  of  the  Engineer,  or  to  proceed  with  the  same  as 
rapidly  as  the  said  Engineer  shall  direct,  that  it  shall  be  lawful  for  the  said 
Sewer  Commission,  after  three  days'  written  notice  of  their  intention  so  to  do, 
by  serving  the  notice  on  the  part.  ...  of  the  second  part  either  personally  or  by 

leaving  a  copy  at usual  place  of  business  or  residence  fand  if  said  party 

of  the  second  part  consist  of  more  than  one  person,  then  by  such  service  upon 
either  of  them),  and  at  the  expiration  of  an  additional  ten  days  thereafter  to 
cancel  said  contract,  and  relet  the  same,  or  proceed  to  complete  the  work  by 
the  purchase  of  material  and  the  hiring  of  labor;  and  if  the  sum  so  paid  for  the 
completion  of  the  said  contract  shall  exceed  the  sum  due  the  part.  ...   of  the 

second  part  under  this   contract,    then  the  said   part of   the  second  part 

and sureties  shall  become  liable   to  the   party  of   the  first   part  for  any 

sum  by  which  the  expense  of  so  doing  the  work  shall  exceed  the  su"m  due  under 
this  contract  as  liquidated  damages,  and  not  by  way  of  penalty,  and  the  said 
contract  shall  thereupon  become  void,  as  to  the  part....  of  the  second  part, 
except  as  to  any  right  of  action  which  may  have  accrued  to   the  party  of  the 

first  part  against  the  part of  the  second  part  and sureties  for  not 

properly  proceeding  with  and  completing  the  work. 

94.  In  consideration  of  the  completion  by  said  party  of  the  second  part, 
of  all  the  work  embraced  in  this  contract,  in  conformity  with  the  specifications 
and  stipulations  herein  contained,  and  in  strict  accordance  with  the  instructions 

of  the   Engineer,    the    City  of   party    of    the    first    part,    hereby 

agrees  to  pay  to  the  said  party  of  the  second  part,  the  prices  named  in  the 
"Proposal"  which  is  hereto  annexed,  and  which  is  hereby  made  a  part  of  this 
contract. 

95.  Payments  for  the  work  shall  be  made  monthly  upon  the  estimate  of 
the  Engineer.     Ten  per  cent,  of  the  amounts  due  will  be  retained  as  a  guaran- 


156  THE   SEPARATE    SYSTEM    OP'    SEWERAGIi. 

tee  against  poor  workmanship  and  materials.  One-half  of  this  reserve  will  be 
paid  as  soon  as  the  work  is  completed  and  accepted  and  the  balance  at  the 
expiration  of  one  year  after  the  acceptance  of  the  work. 

/;/    Witness    Whereof,   the  City  of has  caused  its  name 

to  be  affixed  by thereunto  duly  authorized, 

and  the  said party  of  the  second  part 

h hand,  the  day  and  year  aforesaid. 

Attest  : 


[form  of  bond.] 

BOND. 

KnP70  all  Men  by  these  Presents,    That  7oe . 


are  held  and  firmly  bound  unto  the  City  of 

in  the  sum  of Dollars,  lawful 

money  of  the  United  States  of  America,  to  be  paid  to  the  said  City  of 

,  or  to  its  certain  attorney  or  assigns,  to  which  payment, 

well  and  truly  to  be  made,  we  bind  ourselves,  our  heirs,  executors,  and  admin- 
istrators, and  each  and  every  of  them,  firmly  by  these  presents. 

Signed  and  sealed  with  our  seals,  and  dated  at 

this day  of i .  .  .  . 

The  Condition  of  this  Obligation  is  such,  That  Whereas,  the  said 

ha.  . . . 

entered  into  a  contract  with  the  city  of 

bearing  date  the day  of i which 

said  contract  is  hereunto  attached. 


CHAP.    VIII.  SPECIFICATIONS    AND    CONTKACT. 


N'ow,   T/u-reforc,  If  the  said 

shall  well  and  truly  keep  and  perform   all   the   terms  and  conditions  of  said 

contract,  on part  to  be  kept   and  performed,    and  shall  indemnify 

and  save  harmless  the  said  City  of 

as  therein  stipulated,  then  this  obligation  shall  be  of  no  effect,  but  otherwise  it 
shall  remain  in  full  force  and  virtue. 

L.    S. 

L.    S. 

L.   S. 

L.    S. 


CHAPTER  IX. 

CONSTRUCTION. 

Before  staking-  out  the  line  it  will  be  necessary  to  find 
out  the  location  of  whatever  g^as,  water,  and  sewer  pipe  may 
have  been  previously  laid.  This  is  not  always  easily  accom- 
plished. Work  of  this  kind  is  frequently  done  under  the 
direction  of  the  so-called  "practical  man,"  who  scorns 
"theory  and  science,"  and  whose  sublime  confidence  in  his 
own  ability  is  only  equaled  by  his  capacity  for  eng^ineering- 
blunders,  as  exhibited  in  bad  plans  and  worse  construction. 

One  of  the  most  annoying"  thing^s  to  be  met  with  in 
locating"  sewers  is  to  find  water  and  gfas  pipes  running-  hap- 
hazard throug"h  the  streets,  havings  been  put  down  without 
system  or  sense,  and  worse  than  all,  to  find  that  no  map  or 
record  of  their  location  has  ever  been  made. 

Importance  of  Record. — The  value  of  the  work  will 
larg^ely  depend  on  the  facility  and  accuracy  with  which  the 
exact  location,  laterally  and  vertically,  of  every  part  of  the 
system  can  be  indicated;  and  hence  in  the  construction  notes 
such  methods  must  be  used  as  will  be  rapid,  accurate  in  the 
g"reatest  possible  deg"ree,  and  least  liable  to  mistakes  in 
recording". 

The  following"  described  methods  have  been  found  to 
g"ive  g"ood  results: 

Alignment. — First,  let  the  centre  line  of  the  sewer  be 
located  carefully  on  the  g"round  with  a  transit,  making"  a 
study,  as  the  line  is  extended,  of  the  map  of  g"as,  water  and 
sewer  pipes  previously  referred  to. 

All  measurements  should  be  made  with  a  steel  tape,  and 
all  notes  made  to  the  centre  line  of  the  sewer  as  run. 
Since  it  would  be  impossible  to  preserve  this  line,  however. 


CHAP    IX. 


CONvSTKUCriOX. 


159 


during-  the  construction,  no  stakes  need  be  left  in  it,  but 
stakes  sliould  be  set  to  the  rig-ht  or  left  a  uniform  distance  of 
about  one  foot  g-reater  than  half  the  width  of  the  proposed 
trench.  This  will  bring-  them  within  the  space  on  the  bank- 
usually  left  clean  for  the  workmen  to  pass  and  repass  in 
handling  material,  etc.  The  position  of  stakes  is  shown  in 
Plate  I. 

The  stakes  should  be  set  at  uniform  distances  of  about 
twenty-five  feet  apart.  They  should  be  about  one  inch 
square  in  section,  square  on  top,  and  of  such  a  leng-th  that 
they  can  be  driven  flush  with  the  surface  of  the  street. 
Where  extreme  accuracy  is  required  it  will  be  well  to  indi- 
cate the  precise  point  in  the  stake  by  a  tack  driven  into  its 
top;  but  ordinaril}^  with  the  size  of  stake  indicated,  this  will 
be  unnecessary.  The  offset  line  should  uniformly  be  taken 
on  the  same  side  to  avoid  confusion,  and  the  notes  should 
indicate  the  side  on  which  it  is  taken. 


Reference  Points. — The  line  is  best  located  by'observing- 
to  the  nearest  tenth  of  a  foot  the  station  which  is  intersected 
by  the  prolong-ed  lines  of  brick  walls  or   other   permanent 

Sta. 


640.4 


Sta. 
600 


Sta. 
500 


37  ft. 


Fig.    3. 


BRICK 
HOUSE. 


160  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

lines  which  are  clearly  defined,  and  also  the  distance  from 
the  corner  of  the  building-,  the  line  of  whose  wall  is  pro- 
long-ed,  to  the  centre  line  of  the  sewer  at  the  station  observed 
as  above.  (See  Fig".  3;  the  prolong-ation  of  the  brick  wall 
intersecting-  the  true  line  at  station  (U0.4,  and  being-  at  this 
point  37  feet  distant  from  the  corner  of  the  building.)  This 
will  be  found  a  much  more  satisfactory  location  than  the 
ordinary  method  of  tie  lines  or  focal  co-ordinates,  requiring- 
less  description  in  the  notes,  and  gMving  a  sharper  determi- 
nation of  the  point.  It  may  be  supplemented  at  street  inter- 
sections and  chang-es  in  direction,  however,  by  the  latter 
method  with  advantag-e. 

Two  rules  should  be  kept  in  mind  in  this  method  of  loca- 
tion, viz.:  Never  record  a  measurement  to  the  offset  line,  as 
it  is  only  for  use  temporarily.  Never  leave  a  permanent 
stake  in  the  true  line,  as  it  may  lead  to  confusion. 

There  will  be  no  difficulty  in  finding  the  offset  stakes, 
even  thoug-h  they  be  driven  flush  with  the  surface  of  the 
ground,  as,  having  a  starting-  point,  nearly  the  precise  loca- 
tion can  be  determined  by  measurement.  When  the  streets 
are  paved  with  stone  pavement,  a  block  can  be  removed  and 
the  stake  driven,  and  then  the  stone  replaced. 

At  chang-es  in  direction,  the  angular  deflection  should  be 
recorded,  and  also  the  location  of  the  intersecting-  tangents, 
with  reference  to  prominent  and  permanent  objects. 

Curves. — When  the  angular  deflection  is  slight,  no  curve 
will  be  required  in  the  orig-inal  location  on  the  g-round,  but 
the  notes  should  g-ive  the  offset  to  be  made  from  the  inter- 
section of  tangents,  and  from  short  stations  equally  distant 
from  it  on  either  side.  The  exact  location  of  the  centre  line 
can  then  be  determined  by.  drawing-  a  tape  on  the  tang-ents 
either  way  from  the  intersection  of  tang-ents,  and  measuring- 
the  offset  required  from  the  proper  points  on  the  tape,  with 
an  offset  rod. 


CHAP.    IX.  CONSTKUCTION.  161 

When  the  anovular  deflection  is  considerable  the  curve 
should  be  run  by  transit  or  chord  deflections  in  stations  of 
twenty-five  feet.  Intermediate  points  can  be  interpolated  in 
construction  by  ordinates  from  the  chord. 

The  method  above  indicated,  when  faithfully  pursued, 
will  enable  us  to  replace  any  point  in  the  transit  line  with 
precision. 

Transit  Notes. — The  transit  notes  should  indicate 
approximately  the  distance  from  the  sewer  line  to  the  build- 
ing's on  either  side,  where  they  stand  back  from  the  street 
line.  This  may  be  taken  by  a  g-ood  transit  man  with  suffi- 
cient accurac}^  by  the  eye,  aided  b}^  an  occasional  measure- 
ment. 

The  intersection  of  both  lines  of  all  crossing-  streets 
should  be  noted  by  station  on  the  transit  line,  and  also  the 
offset  from  the  transit  line  to  ang"les  in  the  street  line.  All 
crossing's  of  streams  should  also  be  taken,  and  whatever 
notes  are  necessary  to  completely  determine  and  indicate  the 
physical  characteristics  of  the  territory. 

The  location  should  proceed  from  the  outlet  upward 
toward  the  hig^her  levels  of  the  system,  and  the  various  trib- 
utary branches  should  be  tied  to  one  another  and  to  the  main 
lines  as  often  as  possible,  as  a  check  on  the  work  and  as  a 
g-uide  in  platting-  the  finished  map. 

Level  Notes. — The  transit  party  should  be  followed  by 
the  leveler  and  assistants.  The  surface  elevation  should  be 
taken  on  the  true  line,  which  can  readily  be  obtained  from 
the  stakes  left  by  the  transit  party  by  an  offset  measured  by 
the  leveling-  rod,  or  in  ordinary  cases  can  be  determined  with 
sufficient  accuracy  by  the  eye,  after  a  little  practice.  The 
levels  should  be  carefully  checked  at  each  bench-mark,  as 
described  on  pag-e  61.  In  cases  where  there  is  a  sharp 
transverse  slope  to  the  surface  of  the  g-round,  or  when  the 


162  THE    SEPARATK    SYSTEM    OF    SEWERAGE. 

building-s  on  one  side  of  the  street  are  considerabl\"  elevated 
or  depressed  below  the  street  level,  this  should  be  carefully 
noted,  and  also  the  depth  of  basements,  and  any  conditions,  a 
knowledg^e  of  which  will  aid  in  g"iving  a  proper  seweragfe 
S3' stem  to  each  Ijuilding-. 

The  level  of  all  streams  should  be  taken,  and  so  far  as  it 
can  be  ascertained,  the  approximate  level  of  the  g"round 
water.  This  can  be  ascertained  with  tolerable  precision  by 
observing^  the  condition  of  wells  bordering-  the  street,  when 
such  can  be  found.  The  levels  of  water  in  these  should  be 
taken  at  intervals,  and  on  both  sides  of  the  street,  as  the 
subterranean  water  surface  may  have  a  sharp  decline  in  the 
direction  of  its  natural  drainag^e  basin. 

In  cases  where  it  is  probable  that  the  construction  work 
will  shortlv  follow  the  adoption  of  a  plan  and  where  the 
physical  character  of  the  territory  is  sharply  defined,  and 
the  drainag-e  lines  are  apparent  on  a  superficial  inspection, 
the  preliminary  and  final  survey  ma}'  be  combined  in  one 
with  economy. 

Profiles.  —  The  transit  and  level  notes  being-  complete, 
profiles  of  the  several  lines  should  be  made  to  a  larg-e  scale, 
showing-  the  surface  and  grade  lines,  intersecting-  streams, 
etc.  It  will  save  the  eng-ineer  much  anno^-ance  if  the  con- 
tractor be  furnished  a  duplicate  of  the  profile  or  a  statement 
of  the  cuts  at  the  several  stations  as  he  can  then  intellig-ently 
plan  his  work  from  the  outset  without  further  questions. 
The  ordinary  profile  paper,  known  to  the  trade  as  Plate  A, 
will  be  found  suitable  for  this  work,  and  a  convenient  scale 
will  be  one  foot  verticall}'  for  each  one-fourth  inch,  and  one 
hundred  feet  horizontally  for  each  two  and  one-half  inches,  to 
which  the  Plate  is  adapted.  Cuts  can  be  taken  from  this 
scale  with  tolerable  accuracy,  and  they  will  serve  as  a  check 
on  those  found  by  computation. 


CHAP.   IX. 


CONSTKUC'IION. 


163 


\Vorking  Map. — The  plan  being-  definitely  decided  upon, 
and  the  profiles  made  as  described,  a  roug-h  map  should  be 
made  for  use  in  construction,  showing-  position  and  size  of 
sewers,  location  of  man-holes,  lamp-holes,  flush  tanks,  and 
other  accessories,  and  kept  in  the  office  for  convenient  refer- 
ence during-  the  prog-ress  of  the  work. 

Note  Books. — Each  constr-ucting-  engineer  should  be  fur- 
nished with  a  field  book,  arrang-ed  something-  as  follows: 


LEFT    HAND    PAGE. 


RIGHT    HAND    PAGE. 


Station. 

Surface. 

Grade. 

Cut. 

Construction  Notes. 

The  four  columns  at  the  left  should  be  filled  from  the 
notes  in  the  office,  and  the  construction  notes  should  be 
taken  as  the' work  proceeds. 

Construction. — It  is  g-enerally  best  to  commence  the  con- 
struction at  the  outlet  and  work  toward  the  hig-her  levels. 
When  this  is  done,  the  spig-ot  of  each  pipe  is  easil}^  inserted 
in  the  socket  of  that  already  laid.  There  is  also  no  tendency 
of  the  pipes  to  crawl  away  from  the  work  or  to  open  at  the 
joints  before  the  cement  may  be  entirely  set. 

In  some  cases,  however,  where  the  grades  are  flat,  and 
water  is  found  in  larg-e  quantities  in  the  trench,  the  pipes 
can  be  laid  from  above  downward  with  advantag-e,  as  the 
water  can  thus  be  drawn  away  from  the  pipe  into  the  lower 
levels  of  the  trench  and  then  pumped  out  without  interfering- 
materially  with  the  laying-  of  the  pipe.  The  pipe  should  be 
laid  in  each  case  with  sockets  up  or  toward  the  summits,  and 


164  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

spig^ots  down  or  toward  the  outlet;  and  when  the  work  pro- 
ceeds from  above  there  is  more  difficulty  in  makings  proper 
joints  and  in  inserting"  the  gasket. 

The  pipe  should  be  supported  entirely  on  its  cylindrical 
part,  as  shown  in  Plates  I  and  X,  a  recess  being-  formed  to 
receive  the  socket  and  the  cement  joint. 

Pipe  Laying. — The  organization  of  the  gang  for  work 
may  be  as  follows: 

The  earth  can  be  removed  from  the  trenches  to  a  depth 
of  about  the  centre  of  the  pipe  by  common  laborers.  The 
pipe  laying"  gang  should  be  preceded  by  men  trained  to  the 
purpose,  whose  business  it  is  to  shape  the  trench  for  the 
pipe.  In  laying  the  smaller  sizes,  the  pipe  layer  will  need  no 
helper  in  the  trench,  but  can  receive  the  pipe  from  his  helper 
on  the  bank,  and  place  them  unaided.  In  laying  pipe  of 
larger  size,  he  should  sit  or  stand  astride  of  the  pipes  already 
laid,  and  his  assistant  should  receive  the  pipes  from  above 
and  assist  in  placing  them. 

The  joints  should  be  cemented  b}^  a  person  specially 
trained  for  the  purpose.  This  can  best  be  done  by  the 
hands  encased  in  rubber  mittens  or  gloves,  and  they  should 
be  wiped  something"  as  a  plumber  wipes  a  joint. 

After  the  joints  are  cemented,  the  pipe  should  be  care- 
fully bedded,  and  all  Y  branches  carefulh^  packed  and  cov- 
ered by  a  trusty  man  in  advance  of  the  regular  back-filling 
gang. 

When  the  depth  of  excavation  is  considerable,  and  the 
streets  narrow,  or  the  buildings  close  to  the  street  line,  Y 
branches  should  be  more  elevated  than  when  opposite  con- 
ditions are  found. 

Various  mechanical  devices  have  been  proposed  for 
ensuring  the  concentricity  of  the  pipes.  It  is  doubtful  if 
they  are  of  any  great  benefit,  however.     Pipes  which  are  not 


CHAP.    IX.  CONSTKUCTIOX.  165 

truly  formed  should  be  rejected.  Pipes  which  have  too 
loosely  fitting-  spig-ots  and  sockets  should  also  be  rejected,  as 
any  imperfection  in  form  is  less  apparent  and  the  axes  of  the 
pipes  when  laid  are  less  likely  to  coincide.  Since  the  flow 
rarely  rises  above  the  horizontal  diameter  of  the  sewer, 
particular  care  should  be  taken  to  have  its  invert  as  perfect 
as  possible. 

With  g"ood  management  on  the  part  of  the  contractor, 
sewers  of  vitrified  pipe  of  small  diameter,  laid  in  trenches  of 
the  depth  usually  necessary,  can  be  laid  much  more  rapidly 
than  sewers  of  larg-er  diameter,  the  rate  of  progress  being 
limited  in  either  case  by  the  work  of  one  gang-  of  pipe  layers 
or  brick  layers.  Rapid  and  carefully  systematized  work  by 
the  engineer  is  therefore  required,  who  should  take  personal 
charge,  as  the  decisions  constantly  needed  in  its  progress, 
the  locating-  and  recording-  of  junctions  and  similar  work 
cannot  be  left  to  an  inspector.  A  sufiicient  number  of  junc- 
tions should  be  inserted  to  meet  all  future  demands.  Con- 
nections by  cutting  into  the  pipes  where  no  junctions  are 
placed  can  be  made  with  about  the  same  facility  as  if  the 
pipes  were  of  plate  glass,  and  if  so  made  will  ruin  the 
sewers.  A  perfect  record  of  everything-  pertaining-  to  the 
work  should  be  made  for  future  reference. 

Depth. — The  depth  to  which  sewers  should  be  laid  in 
the  street  will  be  determined  by  local  conditions.  In  the 
closely  built  business  portions  of  towns,  however,  where  the 
ground  floor  space  is  valuable,  propert}'  owners  frequently 
desire  to  place  water  closets,  urinals,  laundries,  etc.,  in  the 
basement,  and  although  this  is  not  a  desirable  place  for  them 
it  sometimes  becomes  necessary  to  adopt  this  course  as  the 
lesser  of  two  evils. 

Pipes  should  never  be  laid  under  basement  floors  when 
it  can  be  avoided,  but  should  enter  the  basement  just  above 


166  THE    SKPAKATE    SY.STEM   .OF    SEWERAGE. 

the  floor  and  be  supported  by  substantial  iron  brackets  or 
hang-ers. 

In  cases  where  it  is  necessary  to  locate  plumbing"  fix- 
tures in  basements  the  following-  will  be  a  reasonable  allow- 
ance for  the  depth  of  the  sewer  in  the  street: 

Depth  of  basement  below  street  level g  oo  feet. 

Inclination  of  house  sewer,  1-60  (50  feet) 83 

Diameter  of  street  sewer  (8  inches) 67 

It  will  often  be  impossible  to  secure  the  desired  depth. 
The  problem  then  becomes  to  secure  the  maximum  depth 
consistent  with  requisite  grade,  etc. 

It  is  advisable  in  all  cases  to  keep  the  sewers  at  least  six 
or  eig'ht  feet  below  the  street  surface  in  northern  towns,  to 
avoid  water  and  g"as  service  pipes  and  mains. 

There  is  little  danger  of  sewers  freezing,  even  thoug^h 
they  be  laid  quite  near  the  surface. 

Grade  Line. — The  pipe  should  be  laid  to  line  and  grade 
indicated  by  stakes  driven  in  the  bottom  of  the  trench,  the 
top  of  the  stakes  being-  to  exact  line  and  g-rade.  These 
should  be  set  in  advance  of  the  final  shaping-  of  the  trench,  in 
the  following-  manner:  The  line  is  determined  by  laying-  an 
offset  rod  across  the  trench  at.  the  offset  stakes,  which  were 
set  in  the  final  location,  and  setting-  the  stake  in  line  by  a 
plumb-bob.  The  stake  should  be  driven  to  g-rade  by  a  self- 
reading  rod,  read  directly  from  the  level  whose  elevation 
above  the  assumed  datum  should  be  carefully  checked  at 
each  bench  mark.  No  setting  of  g-rade  peg-s  by  measure- 
ment of  cuts  from  the  surface  should  be  allowed.  A  con- 
venient and  cheap  rod  is  shown  in  Plate  I.  Sixteen  feet  will 
be  found  a  convenient  lengfth. 

Bracing  and  Sheet  Piling. — In  many  soils  it  will  be 
necessary  to  protect  the  sides  of  the  trench  from  caving"  by 
timber  and  braces.  A  very  g-ood  method  of  doing-  this  is 
shown  in  detail  in  Plate  IV.     The  iron  screws  will  be  found 


From  Photograph  of  Sheet  Pihng. 


CHAP.   IX.  COXSTKUCTIOX.  HV.i 

a  great  saving-  over  the  ordinary  method  of  cutting  timber 
shores,  which,  in  many  cases,  can  be  used  but  once,  and  are 
liable  at  any  time  to  become  loosened.  The  iron  screws  can 
be  used  any  number  of  times,  will  lit  any  width  of  trench 
within  reasonal)le  limits,  can  be' quickly  placed  and  removed, 
without  jarring'  the  trench,  and  can  be  tig'htenedat  any  time, 
without  the  trouble  and  risk  of  removing  a  short  one  and 
inserting  a  longer  one  in  its  place.  One  hundred  screws  of 
assorted  lengths  make  a  fair  outfit  for  one  gang  of  pipe  lay- 
ers in  ordinary-  work. 

The  method  of  bracing  and  sheet  piling  can  be  better 
understood  from  a  study  of  the  drawing  than  from  a  written 
description.  It  requires  considerable  experience  to  place  it 
and  remove  it  quickly  and  without  damage  to  the  material. 
By  the  use  of  this  method  of  bracing  and  sheet  piling,  the 
driest  sand  and  gravel  can  be  excavated  about  as  cheaply  as 
soil  sufficiently  tenacious  to  support  itself,  in  trenches 
exceeding  seven  or  eight  feet  deep,  thoug'h  the  sides  of  the 
latter  need  no  protection. 

The  drawing"  shows  two  rows  of  piling;  these  can  be 
increased  to  three  or  four,  or  still  more,  if  necessary. 
Up  to  a  depth  of  eight  or  nine  feet  one  row  of  piling,  in  con- 
nection with  the  horizontal  planking,  will  be  sufficient. 

The  following  bill  of  material  may  be  of  service: 

SINGLE  ROW  OF  SHEET  PILING. 

This  will  be  sufficient  up  to  a  depth  of  eight  or  nine  feet. 
Each  section  of  sixteen  feet  in  length  requires   the   fol- 
lowing material: 

LUMBER. 


10  pieces  2x10,  16  feet  long. 
36       "      ixlO,    7     "        " 

i       "      2x  8,    7     "       "  550  feet  B.  M. 

4:       "      3x  6,  16     " 

4       "      3x  6,     1     " 


170  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

IKON  SCREWS. 

2  screws  36  inches  long"  (closed). 

2       "        24       "  " 

The  above  bill  requires  a  trench  four  feet  in  width  at 
the  top,  and  g-ives  a  clear  space  at  the  horizontal  diameter  of 
the  pipe  of  forty  inches,  and  between  the  horizontal  timbers 
a  clear  space  of  thirty-four  inches.  This  will  be  sufficient 
for  a  pipe  eig"hteen  inches  in  interior  diameter.  For  larger 
sizes  the  leng^th  of  the  screws  must  be  increased,  and  for 
smaller  sizes  the  trench  may  be  somewhat  narrower. 

DOUBLE  ROW  OF  SHEET  PILING. 
This  will  be  sufficient  up  to  a  depth  of  thirteen  or  four- 
teen feet. 

Each  section  of  sixteen  feet  in  length  requires: 

LUMBER. 

10  pieces  2x10,  16  feet  long-.  \ 

72       "      1x10,    7     "       "  / 

8       "      2x  8,    7     "       "  ;      829  feet  B.  M. 

8       "      3x  6,  16     "       "  \ 

6       "      3x  6,    1     "       "  / 

IKOX  SCREWS. 

2  screws  36  inches  long-  (closed). 
1         "       30 

1  "       24       "         " 

2  "       20       "         " 
2        "       14       "         " 

The  above  bill  is  fig"ured  for  a  trench  four  feet  wide  at 
the  top,  and  g-ives  a  clear  space  at  the  horizontal  diameter  of 
the  pipe  of  thirty  inches,  and  a  clear  space  between  the 
lower  horizontal  timbers  of  twenty-four  inches.  This  will 
be  sufficient  for  pipes  of  twelve  inches  in  diameter  and  less. 
For  larg-er  sizes  the  width  of  excavation  should  be  increased. 


PLATE   IV. 


CHAP.  IX.  CONSTRUCTION.  171 

In  heavy  ground  the  leng-th  of  the  horizontal  timbers 
may  be  reduced  to  fourteen  feet  or  twelve  feet  with  advan- 
tag"e,  or  an  extra  set  of  uprigfhts  may  be  used,  dividing-  the 
sixteen  foot  sections  into  thirds  instead  of  into  halves. 

Inspection  of  Material. — All  sewer  pipe  should  be 
inspected  as  fast  as  it  is  delivered  at  the  work,  and  imperfect 
pipe  should  be  plainly  and  indelibly  marked  and  immediately 
removed.  The  eng^ineer  should  also  carefully  scrutinize  all 
pipes  as  they  are  passed  to  the  pipe  layer,  making  sure  that 
none  which  may  have  been  broken  since  the  formal  inspec- 
tion are  laid  in  the  trench.  The  subsequent  breaking-  or 
g^iving-  way  of  a  sing-le  section  of  pipe  may  cause  a  g-reat 
amount  of  damage. 

All  other  material  should  be  inspected  by  the  eng-ineer 
in  a  similar  manner,  and  that  which  is  unfit  for  use  promptly 
removed. 

Location  of  Y  Branches. — Property  owners  should  be 
consulted  as  to  the  position  in  which  they  wish  their  Y 
branches  placed,  and  it  would  be  well  to  send  them  some- 
what in  advance  of  the  construction  a  printed  notice.  If  no 
return  is  made  by  the  property  owner,  the  eng-ineer  should 
locate  the  junction  as  appears  most  convenient  for  the  prop- 
erty. 

The  position  of  all  Y  branches  should  be  located  by 
station,  specifying-  whether  they  are  north  or  south,  east  or 
west.  Any  other  location  is  unnecessary  and  confusing-. 
The  location  is  best  made  from  the  centre  of  the  opening-,  as 
shown  in  Plate  I.  This  should  be  taken  to  the  nearest  tenth 
of  a  foot,  and  a  plumb-bob  should  be  used  to  transfer  the 
point  to  the  surface. 

Artificial  Foundation. — When  very  treacherous  soil  is 
encountered  it  will  be  necessary  to  support  the  pipe  on  arti- 
ficial foundation.  When  soil  of  a  less  treacherous  nature  is 
encountered  it  may  be  sufficient  to  remove  the  soil  somewhat 
below  the  grade  line  and  replace  with  clean  gravel. 


172  THE    SEPAKATl-:    SYSTEM    OF    SEWEKAGE. 

Where  artificial  foundation  is  used  as  a  support  for  pipe 
sewers  the  arrang^eraent  should  be  such  as  will  g^ive  a  uni- 
form and  continuous  support  to  the  pipes  throug^hout  their 
leng-th.  If  they  are  not  supported  in  this  manner  they  will 
be  likely  to  fail  in  trenches  of  any  considerable  depth. 

Sometimes  blocks  are  used  to  support  pipes  in  wet 
trenches,  the  pipes  being-  laid  without  bearing-  upon  the 
earth  except  as  a  bearing-  is  secured  b}-  filling  and  tamping- 
after  the  pipes  are  in  position.  Althoug-h  it  is  possible  to 
secure  a  proper  foundation  in  this  way  in  some  cases,  it  is 
usuall}'  a  dangerous  method  since  upon  the  settlement  of  the 
trenches  the  blocks  are  likeh^  to  take  more  than  their  proper 
share  of  the  bearing. 

The  ideal  condition  is  that  in  which  the  lower  semi-cir- 
cumference of  the  sewer  rests  uniformly  upon  an  unyielding- 
support.  When  this  cannot  be  secured  an  effort  should  be 
made  to  support  it  in  such  a  way  that  the  settlement  will  be 
as  little  as  possible  and  the  support  will  offer  a  uniform 
resistance  to  the  sewer  at  all  points  of  its  leng-th. 

Under  some  conditions  a  cradle  such  as  is  shown  in 
Plate  III  may  be  used  with  advantag-e.  In  case  the  cradle  is 
used  as  a  support  for  pipe  sewers  a  layer  of  sand  or  g-ravel 
should  be  interposed  between  the  cradle  and  the  pipe  to  dis- 
tribute the  bearing-. 

PLATE  III. 


^) 


J 
CRADLE. 


PLATE  V. 


'.320|SS^ 


M3M^£^i^^^^^M^7 


SECTION   ON   A  B 


DKTAI  LS 

—  OF  — 

MAN     HOLE. 


..,--■  .--^:,;.....->^SS 


PLATE  VI. 


p!p3C); 


DETAILS  OF  MAN-HOLE. 


PLATE  VII. 


Vertical  Lcngitudinal  Section. 


Horizontal  Section. 


DETAILS  OF   MAN-HOLE    SHOWING    DRAIN    TILE    CONNEC- 
TIONS. 


PLATE  VIII. 


MAN-HOLE  ON   SEWER  OF  LARGE  DIAMETER. 


CHAP.  IX. 


CONSTRUCTION. 


181 


Particular  care  should  be  taken  to  secure  a  firm  founda- 
tion for  man-holes,  flush  tanks  and  lamp-holes,  as  their 
g-reater  weig-ht  may  cause  a  settlement  which  will  break  the 
pipes. 

Man-Holes. — Man-holes  should  be  built  with  an  eig^ht- 
inch  brick  wall.  The}-  should  be  plastered  outside  and 
inside.  The  iron  cover  with  which  the}"  are  surmounted 
should  weig-h  from  300  to  500  pounds.  The  style  shown  in 
Plate  IX  has  g-iven  g-ood  satisfaction  when  made  to  weig-h 
350   pounds.      It  has  the  following-  advantages:      The  least 


CAST-IRON   HEAD   AND  DUST   PAN. 


182  THE    SEPARATE    SYSTEM    OF   SEWERAGE. 

possible  surface  is  exposed  to  traffic.  The  impact  of  pass- 
ing- wheels  comes  well  within  the  base.  The  interior  down- 
ward projecting"  rim  prevents  any  loosened  brick  from  fall- 
ing into  the  sewer. 

It  is  usual  to  hang  a  dust-pan  below  the  perforations  in 
the  cover  to  catch  the  street  detritus  which  may  work 
through  them.  With  good  grades,  however,  there  will  be  no 
danger  of  stoppage  from  this  source  when  they  are  omitted. 

The  method  of  forming  the  bottom  of  man-holes  to  pre- 
serve the  proper  cross-sectional  form  of  the  flow  is  shown  in 
section.  The  method  of  connecting  a  sewer  of  small  diam- 
eter with  a  larger  one  is  also  shown.  Unless  particular  care 
is  taken  in  forming  these  curves,  solid  matters  will  be 
stranded  in  the  man-holes  and  become  offensive.  The  best 
practice  favors  connecting  pipe  sewers  at  man-holes  with  no 
curves  outside  of  the  man-holes. 

Iron  steps  may  be  built  in  the  wall,  or  a  light  portable 
ladder  used  in  ascending  and  descending.  The  steps  are 
most  convenient,  but  are  liable  to  collect  street  detritus  fall- 
ing from  above. 

Flush-Tanks. — Flush-tanks  should  be  built  with  an 
eight-inch  brick  wall,  and  plastered  inside  and  outside  with 
cement  mortar.  The  upper  courses  of  both  man-holes  and 
flush-tanks  are  exposed  to  the  action  of  alternating  frost  and 
moisture  in  an  unusual  degree,  and  to  the  constant  impact  of 
vehicles,  and  with  the  best  of  material  a  four-inch  wall  is  not 
sufficiently  durable. 

The  interior  of  the  flush-tank  should  be  connected 
directl}'  w4th  the  sewer,  independently  of  its  discharge,  by  a 
pipe  of  large  diameter,  as  shown  in  the  chapter  on  Flushing- 
and  Ventilating.  This  will  induce  a  current  of  air  flowing 
along  the  crown  of  the  sewer  from  the  lower  levels  to  pass 
into  the  tank  and  out  throug^h  the  perforations  in  its  cover. 


PLATE  IX. 


IRON     COVER, 
MAN     HOLE 

^'"-P)  —  AND  — 

i  0r 


FLUSH     TANK. 


.i; 


1 


V  i'-y. 


<    IW.  •  ^1  ^^M^feM^^ ''' '  ••-vi■^•■ 


CHAP.  IX. 


CONSTRUCTION. 


185 


No  other  protection  ag^ainst  frost  is  needed.  This  is  also  a 
material  aid  in  the  ventilation  of  the  sewers.  All  flush-tanks 
should  be  supplied  with  a  dust-pan. 

The  various  types  of  flush-tanks  will  be  more  fullv  dis- 
cussed in  the  chapter  on  Flushing-  and  Ventilation. 

Lamp-Holes. — Lamp-holes  should  have  a  concrete  bed 
under  them  to  prevent  settlement.  The}"  should  be  carried 
up  as  the  trench  is  filled,  and  care  must  be  taken  to  keep  the 
sections  vertical. 

Care  must  be  taken  in  locating-  man-holes,  flush-tanks 
and  lamp-holes  to  avoid  gutters,  crossings  and  other  objec- 
tionable locations. 


OUTLET  CHAMBER. 


Outlets. — Outlets  should  be  arranged  to  discharge  the 
sewage  in  mid-current  where  possible.     This  is  particularly 


186 


THE    SEPAKATK    SYSTEM    OF    SEWERAGE. 


essential  in  the  case  of  broad  and  shallow  streams  with  low 
banks  and  can  usually  be  accomplished  by  a  submerg-ed  iron 
outlet. 

Such  an  outlet  in  process  of  construction  is  shown  by 
the  photo-eng-raving-s,  Plates  XI  and  XII. 

In  this  case  the  position  of  the  outlet  is  ver^-  fortunate, 
being-  on  a  point  of  land  between  two  confluent  streams  one 
of  which  can  be  seen  at  the  right  and  the  other  at  the  left  of 
the  picture  in  Plate  XII. 


PLATE  XIV. 


OUTLET  CHAMBER  WITH  RELEIF  OVERFLOW^. 


PLATE  XV. 


SECTION  OF  BRICK  SEWER  JUNCTION. 


PLATE  XVI. 


MAN-HOLE— BRICK  SEWER. 


CHAP.  IX.  CONSTKUCTION.  105 

House  Sewers. — Experience  with  sewers  of  the  Sepa- 
rate System  demonstrates  that  stoppag'es  in  the  house 
sewers  are  much  more  frequent  than  in  the  hiterals;  and  the 
point  in  the  house  sewers  which  is  particuhirly  liable  to 
obstruction  is  at  the  junction  with  the  street  sewer.  Partic- 
ular care  should,  therefore,  be  taken  in  the  construction  at 
this  point.  The  Y  branch  should  be  properly  elevated  so  as 
to  bring"  the  invert  of  the  house  sewer  above  the  ordinary 
flow  line  of  the  street  sewer,  as  shown  in  Plate  XVII.  The 
curve  should  have  a  sharp  g-rade  and  particular  care  should 
be  taken  to  have  the  spigots  put  squarely  into  the  sockets 
and  the  gasket  well  placed.  No  cutting  and  trimming  of  the 
pipe  should  be  allowed,  as  it  is  impossible  to  make  smooth 
joints  of  terra  cotta  pipe  in  this  way.  Curved  pipe  always 
warps  unevenly  in  the  kiln,  and  from  an  ordinary  stock 
there  will  be  no  difficulty  in  selecting  a  curve  suitable  for 
any  reasonable  case.  Three  or  four  of  these,  slightly 
varying-  in  radius  should  always  be  at  hand. 

A  very  common  defect  is  to  allow  the  centre  or  belh'  of 
the  curve  to  drop  down  and  open  the  joints  before  the}^  are 
hardened,  or  to  do  the  refilling  in  such  a  manner  that  the 
subsequent  settlement  of  the  trench  breaks  the  joints  or 
pipe.  This  can  be  avoided  by  thoroughly  ramming"  the 
earth  up  to  the  horizontal  diameter  of  the  curve  as  it  is  laid 
and  water-tamping  or  ramming  in  layers  above  this. 

House  drains  can  be  very  accuratel}'  laid  in  favorable 
g"round  with  an  ordinary  carpenter's  level  placed  on  each 
pipe  as  laid,  one  end  of  the  level  being  supplied  with  a  gradu- 
ated slide  and  set-screw,  by  which  is  set  off  the  fall  corres- 
ponding to  one  length  of  pipe. 


196  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

Pumping  Stations. — Sewag^e  pumping-  stations  are  often 
necessary  to  protect  the  sewers  from  back  water  during 
hig-h  water  or  to  deliver  the  sewag"e  at  some  point  for  treat- 
ment or  disposal  not  accessible  by  g"ravity  flow. 

It  may  be  necessary  to  operate  them  only  at  certain 
stag^es  of  water  at  the  outlet  and  at  infrequent  intervals  in 
some  cases  and  in  other  instances  they  must  be  operated 
continuously. 

Usually  the  conditions  are  such  that  they  are  operated 
under  a  compai'atively  light  lift. 

The  conditions  under  which  the  plant  is  to  be  operated 
should  control  its  design.  Obviously  a  larg-er  outlay  in  first 
cost  to  secure  a  comparatively  hig-h  duty  and  economy  in 
operation  will  be  justified  in  the  case  of  a  plant  continuously 
operated  against  a  hig-h  lift  than  if  the  plant  is  to  be  operated 
but  a  few  days  each  year  during-  hig-h  water.  In  the  last 
case  the  cost  of  a  days  operation  is  comparatively  imma- 
terial. 

It  is  necessary,  however,  that  the  plant  be  absolutely 
sure  in  its  operation  when  pumping  is  necessary  and  it  is 
desirable  that  the  plant  be  constructed  in  duplicate  so  that 
an  absolute  failure  in  operation  is  improbable. 

For  light  lifls  some  of  the  various  forms  of  centrifug-al 
puijips  are  well  adapted.  They  cost  comparatively  less  than 
others  for  the  same  capacity,  are  not  likely  to  be  obstructed 
by  sewage  and  are  simple  and  sure  in  operation.  The  most 
favorable  results  are  secured  by  setting  them  immersed  in 
the  pumping-  pit. 

The  cut  on  the  opposite  pag-e  shows  a  portion  of  a 
pumping  plant  thus  equipped.  The  pumps  are  two  12-inch 
centrifug-al  pumps  immersed  in  the  pumping-  pit.  They  are 
operated  from  a  counter  shaft  to  which  power  is  supplied  b}- 
two  eng-ines  and  the  eng-ines  are  furnished  steam  from  two 
boilers.  The  arrang-ement  is  such  that  an}'  combination  of 
power  and   pumps   is   possible.       That    is    to    say, — Either 


PLATE  XVII. 


ELEVATION 


SECTION 


IRON  PIPE 
through    House   Wall 


w^ 


^MM^MMZ. 


HOUSE  DRAIN 


SECTION 


BRANCHES,   CURVES 

—  AND  — 

HOUSE    DRAINS. 


CHAP.    IX.  COXSTKUC'riOX.  199 

pump  or  both  pumps  may  be  run  with  either  eng^ine  or  with 
both  engines  and  either  eng-ine  or  both  eng"ines  may  be  sup- 
plied with  steam  from  one  or  both  boilers. 

A  similar  combination  has  also  been  used  by  the  author 
in  which  the  eng-ines  were  directly  connected  without  belt- 
ing" and  with  a  considerable  saving  of  floor  space.  3oih  of 
the  above  described  pumping-  plants  were  desig-ned  for  occa- 
sional pumping-  only. 

Examples  of  more  elaborate  pumping-  plants,  desig-ned 
for  continuous  operation,  are  to  be  seen  at  Boston  and  at 
Pullman. 


CHAPTER  X. 

FLUSHING  AND  VENTILATING. 

In  the  Combined  System. — Any  one  seeing'  the  volume 
of  warm  vapor  rising-  from  the  man-holes  of  an  ordinary 
combined  sewer  on  a  cold  morning-  will  g-et  some  idea  of  the 
immense  quantity  of  g"as  which  constantly  rises  from  a 
sewer;  and  if  he  once  g"ets  a  smell  of  the  ascending-  column 
he  can  form  some  slig-ht  conception  of  its  composition. 

An  examination  into  the  condition  of  the  sewers  will,  in 
most  cases,  at  once  show  the  cause  of  this  enormous  evolu- 
tion of  g-as. 

The  sewers  of  the  Combined  System  are  desig-ned  to 
carry  not  only  the  sewag-e  of  the  town,  but  also  the  storm 
water  from  the  roofs,  yards  and  streets.  Under  these  cir- 
cumstances the  size  of  the  sewer  is  determined  solely  by  the 
amount  of  storm  water  to  be  provided  for;  the  amount  of 
sewag-e  being-  so  small  in  comparison  that  it  may  be  disre- 
g-arded. 

In  fair  weather,  and  especially  in  the  long-  continued  dry 
weather  in  summer,  the  sewag-e  forms  only  a  very  small 
stream  in  comparison  with  the  capacity  of  the  sewer.  This 
comparatively  small  amount  of  sewag-e  is  spread  out  on  the 
bottom  of  the  larg-e  sewer  and  the  stream  is  shallow  and 
slugg-ish. 

Since  the  capacity  of  a  stream  to  carry  solid  matter 
depends  upon  its  depth  and  velocity  it  is  readily  seen  that 
the  solid  particles  in  the  sewag-e  soon  g-et  stranded  and  the 
sewer  becomes  foul  even  where  street  refuse  is  rig^idly 
excluded  by  the  catch  basin,  which  is  not  often  the  case. 


CHAP.  X.  FLUSHING    AND    VKNTILATIXG.  201 

The  storm  water  from  the  streets  usually  carries  with 
it  a  larg-e  amount  of  detritus,  straw,  leaves  and  sticks.  As 
the  flow  in  the  sewer  produced  by  the  storm  slackens  this 
solid  material  is  stranded,  forming-  small  dams  in  the  sewer. 
These  hold  the  sewage  in  pools,  where  it  decomposes  and 
sends  off  immense  volumes  of  sewer  gas. 

Sewer  gas  contains  sulphuretted  hydrogen,  carbu retted 
hydrogen,  nitrogen,  ammonium  sulphide  and  foetid  organic 
vapor. 

Besides  these  gases,  and  quite  as  much  to  be  dreaded, 
are  the  disease  producing-  micro-organisms,  commonly 
known  by  the  name  of  bacteria,  which  abound  in  the  warm, 
moist  air  of  the  sewers  and  are  carried  wherever  the  sewer 
g-as  penetrates.  Several  diseases  are  known  to  be  produced 
by  bacteria,  and  it  is  highh'  probable  that  the  list  will  be 
increased  as  our, knowledge  in  this  field  is  extended. 

In  any  place  the  struggle  for  life  is  between  the  bacteria 
and  the  human  being.  It  is  a  survival  of  the  fittest  in  any 
environment.  Where  sanitary  matters  are  properly 
attended  to  and  the  environment  is  favorable  for  man  it  will 
be  unfavor^able  for  the  bacteria,  so  the  man  will  live  and  the 
bacteria  will  die.  But  where  sanitary  laws  are  disregarded 
and  the  environment  is  unfavorable  for  man  it  will  be  fav^or- 
able  for  his  enemy,  and  the  bacteria  will  thrive  and  the  man 
will  die. 

The  question  arises — what  remedy  can  be  applied  to 
improve  the  condition  of  the  sewer,  and  to  prevent  or  dimin- 
ish the  dangers  to  health  from  this  source? 

Two  things  are  needed  in  order  to  accomplish  this  end: 
flushing  and  the  ventilation  of  the  sewer.  Thorough  Hush- 
ing will  carry  out  the  accumulations  of  solid  matter  and  dis- 
pose of  the  pools  of  putrefying-  sewage.  Fresh  sew^ag-e  is 
not  very  offensive,  and  if  it  can  be  carried  rapidh'  to  its  out- 
fall before  decomposition  sets  in  it  will  cause  verv  little 
trouble  either  by  becoming-  obnoxious  or  dang-erous.      It  is 


202  THE    SEPARATK    SYSTEM     OF    SEWERAGE. 

the  standing-  pools  of  decomposing-  sewag^e  which  causes 
most  of  the  trouble. 

Flushing-  may  be  accomplished  in  several  ways.  One  of 
the  simplest  of  these  is  to  dam  up  the  sewag-e  by  g-ates  in  the 
sewers  until  the  sewers  are  nearly  or  quite  full  and  then 
suddenly  release  it,  causing-  a  full  strong-  current  in  the 
sewers.  Care  must  be  taken  not  to  hold  the  sewag-e  until  it 
backs  up  into  the  cellers  and  basements  along-  the  line.  To 
prevent  the  possibility  of  this,  g-ates  which  only  partly  fill 
the  sewers  are  used,  so  that  when  the  sewag-e  rises  to  a  cer- 
tain heig-ht  it  flows  over  the  g-ate.  Automatic  g-ates  are  also 
used  which  turn  on  a  horizontal  axis  placed  below  the  centre 
of  the  g-ate,  the  top  turning-  outward  away  from  the  confined 
sewag-e.  When  the  sewer  becomes  nearly  full,  the  pressure 
on  the  part  of  the  valve  above  the  axis  being-  g-reater  than  on 
the  smaller  section  below  the  axis,  the  valve  opens  outwardly 
and  releases  the  sewag-e. 

The  principal  objections  to  the  use  of  g-ates  in  the  sew- 
ers are  that  there  is  a  tendency  to  deposit  the  solid  particles 
on  the  bottom  of  the  sewer  where  the  sewag-e  is  impounded, 
and  that  the  method  cannot  be  applied  to  the  upper  ends  of 
the  sewers. 

At  the  upper  ends  other  devices  must  be  resorted  to. 
One  is  to  collect  the  sewag-e  in  tanks,  which  are  discharg-ed 
automatically  w^hen  full.  Another  is  to  use  automatic  flush- 
ing- tanks  tilled  with  water,  either  by  collecting-  rain  water 
from  the  roofs,  or  from  the  public  water  works.  When  the 
water  supply  of  a  town  is  abundant  the  problem  of  flushing- 
sewers  can  usually  be  easily  solved. 

In  any  Combined  Sewer  there  will  be  a  certain  amount 
of  org-anic  matter  smeared  by  the  floods  on  its  interior  sur- 
face above  the  ordinary  surface  of  the  sewag-e,  and  the 
decomposition  of  this  is  constantly  g-oing-  on,  developing-  a 
considerable  volume  of  g-as.  Added  to  this  is  the  g-as  g-en- 
erated  b}"  the  stag-nant  sewag-e  held  in  pools  by  the  obstruc- 


CHAP.   X.  FLUSHING    AND    VICNTH^AIING.  203 

tions  in  the  sewers.  If  there  are  no  opening's  in  the  sewer 
the  traps  in  the  houses  would  be  forced  by  the  pressure  of 
the  g^ases  produced.  Opening's  are  absolutely  necessary  and 
wherever  there  is  an  opening  the  g"as  will  escape.  To  dis- 
pose of  this  g^as  or  to  mix  it  with  so  larg-e  a  volume  of  air  as 
to  render  it  harmless  is  the  problem  which  presents  itself. 

The  ventilation  of  a  system  of  larg"e  sewers  is  a  difticult 
task,  and  up  to  date  it  has  not  been  satisfactorily  done.  One 
of  the  best  authorities  after  careful  investigation  gave  it  as 
his  opinion  that  the  only  practicable  plan  was — to  use  his 
own  words — "to  just  let  the  stink  out  in  the  middle  of  the 
street."' 

The  use  of  high  chimneys  has  been  strong-ly  recom- 
mended, and  they  have  been  experimented  with  to  a  consid- 
erable extent. 

It  has  been  quite  confidently  stated  that  as  some  of  the 
g'ases  found  in  sewers  are  lighter  than  air  there  will  always 
be  an  upward  draught  in  the  chimney  without  any  artificial 
aid.  Unfortunatelv  this  is  not  the  case,  and  to  insure  a  con- 
stant current  of  air  from  the  sewer  up  the  chimney  some 
means  must  be  employed  to  secure  a  draug^ht.  This  ma}'  be 
accomplished  either  by  a  fire  at  the  foot  of  the  chimne}^  or  a 
fan  or  screw  in  the  chimney  which  is  operated  by  a  steam 
engfine  or  other  power.  When  the  fire  is  used  the  sewer  g'as 
is  usually  passed  throug^h  the  fire.  In  this  thpre  is  an 
element  of  dang-er,  as  leaks  from  the  g'as  mains  into  the 
sewer  are  quite  common  and  explosions  from  this  cause  have 
occurred. 

Owing-  to  the  numerous  openings  into  the  sewers  each 
chimney  affects  only  a  limited  area,  so  that  an  extended 
system  of  sewers  would  need  many  chimneys.  The  cost  of 
these  chimneys  and  of  running  the  fires  in  them  pi'ohibits 
their  use,  except  in  special  cases.  This  system  can  be 
made  efficient  if  we  disreg"ard  expense,  but  eng-ineers  soon 
find  that  the  item  of  expense  is  one  of  the  most  important 


204  THE   SEPARATE   SYSTEM    OF    SEWERAGE. 

considerations  in  any  eng-ineering-  project,  especially  if  it 
relates  to  sanitary  matters  which  are  to  be  decided  by  the 
public. 

Another  plan  is  to  ventilate  the  sewers  by  running-  an 
untrapped  branch  up  throug^h  each  house,  relj'ing-  upon  the 
heat  in  the  house  to  create  an  up  draug-ht  in  the  pipe.  This 
would  be  an  efficient  way  of  ventilating-  sewers,  but  it 
g-reatlv  increases  the  dang-er  from  them.  A  leak  in  the  soil 
pipes,  or  the  emptying*  of  a  trap  by  evaporation  or  syphon- 
ag-e  (and  both  of  these  conting-encies  are  much  more  common 
than  is  usually  supposed)  makes  the  house  itself  a  ventilator 
for  the  sewer. 

The  rain  water  conductors  have  sometimes  been  used  as 
sewer  ventilators,  but  this  releases  the  sewer  g-as  in  too 
close  proximity  to  the  windows  of  the  upper  story  of  the 
house  and  is  a  dang-erous  practice. 

One  of  the  best  plans  is  to  carry  up  an  untrapped  pipe 
on  the  outside  of  the  house  to  a  sufficient  heig-ht  above  the 
roof.  \i  this  plan  could  be  g-enerally  adopted  on  any  line  of 
sewers  it  would  afford  one  of  the  best  solutions  to  the  ven- 
tilation problem. 

Various  chemical  processes  for  treating-  sewer  g-as  in 
the  sewers  have  been  proposed,  such  as  liberating-  chlorine 
g-as,  or  sulphurous  acid  in  the  sewers.  These  methods  have 
been  tried  on  a  small  scale  but  the  results  have  not  thus  far 
been  encourag-ing-. 

A  more  successful  plan  has  been  to  purify  the  sewer  g-as 
as  it  comes  from  the  sewers  by  passing-  it  throug-h  loosely 
packed  charcoal.  This  has  been  tried  on  a  larg-e  scale  and 
has  been  fairly  satisfactory  althoug-h  quite  expensive. 

A  patent  was  taken  out  in  1S5S  for  purifying-  sewer  air 
by  passing-  an  electric  current  throug-h  it. 

In  the  Separate  System. — We  have  thus  far  been  deal- 
ing- with  the   "Combined  System"  of  sewers.       Where   the 


CHAP.    X.  FLUSHING    AND    VICNTH^ATING.  205 

Separate  System  is  employed  the  problems  of  flushing-  and 
ventilation  are  materially  simplified. 

As  has  been  already  stated  the  amount  of  sewag^e  is  so 
small  in  comparison  with  the  storm  water  as  to  be  neg-lectcd 
entireh'  in  computing-  the  sizes  needed  in  a  Combined  Sys- 
tem. This  being-  the  case  it  is  readily  seen  that  the  neces- 
sary size  of  separate  sewers  is  small  in  comparison  with 
those  of  the  Combined  System,  and  hence  much  less  water  is 
needed  for  flushing". 

Ag-ain,  since  the  flow  of  sewag-e  is  approximate!}'  con- 
stant and  not  fluctuating-  between  the  wide  limits  of  the  flow 
of  storm  water,  the  sizes  of  the  pipes  may  be  desig-ned  so 
that  the  flow  of  the  sewag-e  will  keep  the  mains  in  proper 
condition,  while  the  upper  ends  can  easily  be  flushed  by 
means  of  automatic  flushing  tanks  of  small  size,  compared 
with  those  needed  on  the  larg-e  sewers  of  the  Combined  Sys- 
tem. 

A  tank  placed  at  each  dead  end  and  adjusted  to  dis- 
charge once  every  day  will  g-enerally  keep  the  sewers  well 
flushed. 

To  thoroug-hly  flush  a  sewer  requires  a  volume  of  water 
sufficient  to  fill  the  sewer  for  a  considerable  distance.  The 
best  results  would  be  obtained  if  the  sewer  could  for  a  time 
be  filled  its  entire  leng-th,  so  as  to  flush  all  of  the  upper  part 
of  the  pipe  as  well  as  the  lower.  This  would  not  only 
cleanse  the  pipe,  but  materially  aid  in  its  ventilation  by 
securing-  an  entire  chang-e  of  air  in  the  sewer. 

When  flush  tanks  are  used  to  flush  the  sewers,  if  the 
discharg-e  from  the  tank  is  sufficiently  rapid,  the  flushing- 
will  be  thoroug-h,  for  a  g-reater  or  less  distance,  depending- 
upon  the  g-rade  of  the  sewer.  Gradually,  however,  the 
water  will  lose  its  velocity,  and  the  flushing-  effect  will  be 
less  and  less  until  it  amounts  to  but  verj^  little. 


206  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

Roof  Water. — The  storm  watei"  from  the  roofs  may  be 
utilized  for  flushing-  bj  connecting-  a  limited  number  of  rain 
water  conductors  with  the  sewers  at  the  upper  ends  of  the 
lateral  branches. 

When  roof  water  is  used  for  flushing  a  difficulty  arises 
in  adjusting-  the  amount  of  water  to  be  admitted.  When  the 
sewers  are  first  completed,  much  more  water  will  be  needed 
to  flush  them  than  will  be  required  after  their  use  has 
become  general,  and  the  flow  of  sewage  has  more  nearly 
reached  its  maximum.  But  having  once  permitted  the  roof 
water  from  any  building  to  be  turned  into  the  sewers  it  is 
difficult  to  shut  it  out  when  the  proper  time  comes. 

When  the  sewers  are  flushed  by  connecting  the  dead 
ends  of  the  sewers  with  the  water  mains,  the  amount  of 
water  can  readily  be  adjusted  to  suit  the  requirements  in 
each  case.  The  water  from  the  mains  may  be  admitted  to 
the  sewers  by  a  direct  pipe  connection,  provided  with  a  suit- 
able valve,  or  it  may  be  taken  from  a  h^^drant  and  carried 
through  a  hose  to  a  lamp  hole  at  the  dead  end  of  the  sewer, 
which  in  this  case  should  be  constructed  as  shown  in  Plate  I. 

As  the  small  sewers  are  of  smooth  earthenware  pipes 
they  are  much  easier  kept  clean  than  the  rough  interior  sur- 
faces of  the  large  brick  sewers  and  flushing  will  be  more 
effective. 

The  ventilation  of  the  separate  sewers  is  a  much  sim- 
pler matter  than  in  the  case  of  the  Combined  System, 
When  properh'  designed  and  constructed  there  are  no  pools 
of  decomposing  sewage  standing-  along  the  lines,  and  as  a 
consequence  there  is  much  less  evolution  of  gas  and  hence 
much  less  need  of  special  appliances  for  ventilation. 

The  rush  of  water  from  the  flush  tanks  changes  the  air 
in  the  upper  ends  of  the  sewers,  and  the  fluctuations  of  flow 
in  the  mains  is  an  important  factor  in  changing  the  air  in  the 
sewers  bv  driving  out  the  foul  air  as  the  sewag-e  rises  at  the 


PLATE  XVIII. 


U^ 


u 


CHAP.    X.  FLUSHING    AND    VKNTH-ATING.  '20t> 

time  of  its  maximum  daily  flow,  and  refilling-  the  pipes  with 
pure  air  as  the  flow  falls  to  its  minimum. 

Any  of  the  methods  of  ventilation  which  can  be  used  on 
the  Combined  System  are  available  for  the  Separate  System, 
and  as  the  amount  of  air  to  be  moved  is  much  less  they  will 
be  more  effective. 

The  man-holes,  flush-tanks  and  lamp-holes,  when  pro- 
vided with  perforated  covers,  as  shown  in  the  plates,  will 
assist  in  the  ventilation  for  the  street  sewers  of  the  Separate 
System.  The  house  drains,  however,  need  some  special 
arrang-ement  for  that  purpose.  An  opening-  from  the  house 
drain  to  the  air  is  necessary,  not  onl}'  for  ventilation  but  to 
prevent  emptying-  the  traps  by  syphoning-  when  the  sewer  is 
flushed. 

The  simplest  method  of  accomplishing  the  ventilation  of 
the  house  drains  and  at  the  same  time  of  the  sewers  them- 
selves, is  to  extend  the  main  drain  upward  and  out  through 
the  roof,  unbroken  by  a  trap  in  any  portion.  In  this  case  it 
serves  the  double  purpose  of  soil  and  ventilating  pipe,  and 
the  air  which  passes  into  the  street  sewers  at  man-holes  sup- 
plies the  draug-ht  upward  along  the  street  sewers,  and  out 
through  these  and  their  upward  extensions  In  this  case 
the  isolation  of  the  interior  of  buildings  from  sewer  air 
depends  solely  upon  the  trap  under  each  fixture.  Where 
street  sewers  are  properly  constructed  on  the  Separate  Sys- 
tem, and  properly  cared  for,  this  method  has  proved  entirely 
satisfactory.  It  certainly  has  g-reat  advantag-es  in  simplicity 
and  facility  of  arrang^ement. 

Where  the  sewers  are  built  on  the  combined  plan  the 
method  of  isolation  shown  in  Plates  XVIII  and  XIX  is  to  be 
preferred.  This  diverts  the  foul  air  currents  from  the 
interior  pipe  and  provides  a  supply  of  fresh  air  for  the 
upward  current  throug-h  the  soil  and  ventilating-  pipe.  If 
the  street  sewers  are  not  properl}'  ventilated  at  frequent 
intervals,    either   by   the    upward    extension   of   exterior  or 


210  THE    SEPARATE    SYSTEM    OE    SEWERAGE. 

interior  unobstructed  pipes  or  otherwise,  there  may  be 
reasons  for  believing-  that  an  isolated  one  may  draw  from 
too  wide  a  territory  and  prove  offensive.  In  this  case  it  is 
advisable  to  dispense  with  any  vent  pipe  communicating- 
directly  with  the  sewer. 

If  we  could  be  perfectly  certain  that  all  the  drain,  waste 
and  soil  pipes  were  perfectly  gas  tight  throughout  their 
whole  length,  and  would  remain  so,  and  that  no  fixture  traps 
w^ould  ever  be  emptied  by  syphoning-,  evaporation,  capillary 
attraction,  or  any  other  of  the  many  w^ays  by  which  traps  do 
g-et  emptied,  we  might  safely  use  untrappcd  house  drains. 
But  taking  the  conditions  as  they  are,  it  seems  to  be  taking- 
too  great  a  risk  to  ventilate  the  public  and  private  sewers 
tlirongh  the  dwellings. 

S.  Stevens  Hellyer,  the  wx'U  known  sanitary  engineer, 
writes  as  follows: 

"Where  the  drains  (house  drains)  are  carried  direct  into  the  sewer,  without 
traps,  the  houses,  through  the  sewer,  are  brought  into  direct  communication 
with  each  other,  /.  e.,  the  air  in  the  drain  of  one  house  can  pass  into  the  drain 
of  another  house.  Contagious  diseases — typhoid  or  what  not — may  be  infect- 
ing a  house,  and  however  isolated  it  may  be  from  other  houses  above  ground, 
it  would  not  be  so  under  ground  with  such  a  system.  The  untrapped  drains 
branching  into  the  sewer  would  form  a  subterraneous  passage  for  the  bad  air 
or  disease  germs — coming  from  the  stools  of  the  infected  patients — between 
house  and  house.  But  when  each  house  drain  is  trapped  off  before  entering 
the  sewer,  an  all  but  impassable  barrier  would  be  placed  between  the  drains,  so 
that  the  houses  would  be  as  much  isolated  under  as  above  ground." 

If  every  house  could  be  thus  provided  with  the  means  of 
ventilation  the  whole  problem  of  the  ventilation  of  sewers 
would  be  simplified,  and  the  provision  for  ventilating  the 
house  drains  would  supply  the  needed  ventilation  of  the 
sewers. 

Man-holes  and  flush-tanks  are  liable  to  be  covered  with 
snow  or  mud  at  times  and  their  efficiency  as  ventilators 
interfered  with.  If  all  house  connections  are  made  in  the 
way  above  described — that  is,  if  there  is  a  free  communica- 


PLATE  XIX. 


V/» 


MAIN    VENTILATING    PIPES    AND    TRAP. 


CHAP.    X.  FLUSHING    AND    VENTILATING.  213 

tion  between  an  uprig-ht  ventilating-  pipe  on  each  premises 
and  the  sewer  proper — we  have  substantially  a  horizontal 
pipe  having  at  frequent  intervals  vertical  pipes  leading-  from 
it.  These  vertical  pipes  are  of  varying-  leng-ths  and  their 
upper  ends  are  at  different  elevations,  covering-  a  rang-e  of 
several  hundred  feet,  perhaps.  These  vertical  pipes  are 
also  subjected  to  different  conditions.  For  instance  some 
of  them  are  within  building-s  near  artificial  heat,  some  of 
them  are  at  the  south  side  of  building-s  where  the  sun  will 
eft'ect  them,  some  on  the  north  side  where  the  temperature 
is  lower,  some  of  them  are  short  and  some  are  long-.  In 
short,  the  conditions  are  such  that  there  cannot  be  an  equi- 
librium of  pressure  throughout  the  system.  Now,  if  the 
openings  at  the  mouth  of  the  sewer,  at  the  man-holes  and 
flush-tanks  are  relatively  large  enough,  and  the  air  space 
along  the  sewer  toward  the  higher  levels  where  the  house 
connections  are  numerous,  is  relatively  large  enough,  it  ma}^ 
happen  that  there  will  be  an  upward  current  in  all  the  house 
ventilating  pipes,  the  air  being  supplied,  of  course,  through 
the  openings  along  the  sewer  proper.  It  is  probable,  how- 
ever, that  this  rarely  occurs  for  the  reason  that  the  com- 
bined section  of  the  ventilators  is  many  times  the  section  of 
the  air  passage  in  the  sewer  proper  and  consequently  any 
difference  in  pressure  that  may  be  induced  in  the  ventilating 
pipes  by  the  causes  above  cited,  is  more  easily  restored  by 
downward  draughts  in  some  of  the  ventilating  pipes.  It 
may  thus  happen  that  the  short,  cool  ventilating  pipes,  par- 
ticularly at  the  lower  levels  have,  some  of  the  time  at  least,  a 
downward  draught  and  that  the  total  volume  of  air  which 
passes  through  the  system  at  various  points  is  greater  than 
could  be  supplied  through  the  outlet,  man-holes,  etc.,  at  the 
velocity  which  would  be  likel}^  to  be  induced. 


214  THK    SKPARATE    SYSTEM    OF    SEWERAGE. 

Automatic  Flush  Tanks.* — Flush-tanks  are  used  either 
to  collect  the  sewag^e  and  discharg-e  it  rapidly  at  intervals  for 
the  purpose  of  flushing-  the  sewers,  or  to  collect  and  dis- 
charg-e clean  water  for  the  same  purpose.  They  should  be 
automatic  in  their  action. 

This  regular  and  automatic  flushing  is  usually  applied  to 
Separate  Systems,  and  the  diminished  size  of  the  pipes 
renders  it  very  effective.  It  sweeps  down  all  deposits  and 
stranded  matter  from  the  remotest  portion  of  the  system 
into  the  mains,  and  the  ag-g-reg-ate  of  these  discharges  in  the 
mains  from  tanks  differently  timed,  continued  with  the  flow 
of  sewage  proper,  sweeps  it  on  to  the  outlet.  The  more 
reg-ular  flow  in  the  Separate  System  and  consequent  immu- 
nity from  variations  in  air  space  and  pressure  reduces  the 
dang-er  of  forcing-  traps.  The  smaller  air  space  increases 
the  efficiency  of  all  opening-s  in  relieving-  any  pressure 
resulting-  from  such  variations,  and  also  increases  their  effi- 
ciency as  ventilators. 

There  are  many  forms  of  automatic  flush-tanks,  most  of 
which  may  be  classed  under  the  four  following-  varieties:  1, 
Tilting-  Tanks;  2,  Syphon  Tanks;  3,  Valve  Tanks;  4,  Col- 
lapsing Tanks. 

Tilting-  tanks  are  so  desig-ned  that  as  they  lill  the  centre 
of  g-ravity  is  chang-ed,  until  finally  the  equilibrium  of  the 
tank  is  destroyed  and  the  tank  tilts  over  and  empties  itself. 
The  tank  is  so  adjusted  that  when  empty  it  returns  to  its 
proper  position.  A  tilting-  tank  on  a  small  scale  is  shown 
attached  to  the  long-  leg-  of  the  syphon  in  Van  Vranken's 
flush  tank,  Plate  XXI. 

Syphon  tanks  are  discharg-ed  by  means  of  a  syphon. 
They  differ  in  the  devices  for  starting  the  syphon.  In 
places  where  the  sudden  rush  of  a  considerable  quantity  of 


*The  following  descriptions  of  flush  tanks  are  taken  mainly  from  the  manufacturers 
catalogues. 


CHAP.    X.  r LUSHING    AND    VENTILATING.  ^1,5 

water  can  be  secured,  no  device  is  necessary.  Where  house 
sewag"e  is  collected  in  tanks  for  flushing-,  the  rush  of  water 
caused  by  emptying-  a  bath  tub,  wash  tub,  etc.,  will  be  suffi- 
cient to  start  the  syphon.  But  where  the  tank  is  filled  by  a 
stream  of  water  small  enoug-h  to  fill  a  tank  holdings  but  a  feu- 
hundred  g-allons  only  once  in  twenty-four  hours,  some  spec- 
ial arrang-ement  will  be  necessary  to  start  the  syphon. 
This  can  be  done  by  means  of  a  small  tilting-  tank  on  the 
long  leg  of  the  syphon,  as  in  Van  Vranken's  tank;  by  a  sup- 
plementary tank  and  syphon,  as  in  Field's;  by  a  ball  cock, 
increasing-  the  flow  when  the  tank  is  nearly  full,  as  in  Vib- 
bard's;  by  haying-  the  long-  arm  of  the  syphon  movable,  as  in 
Landon's;  by  a  collapsing-  disk  or  tube,  as  in  Chaplin's;  by 
an  automatic  valve  on  the  long^  leg-  of  the  syphon;  by  an 
aspirator;  and  in  various  other  ways. 

Field- Waring  Flush-Tank. — The  syphon  invented  and 
patented  by  Kog-ers  Field  and  improved  by  Col.  Georg-e  E. 
Waringf,  Jr.,  consists  (in  the  form  shown)  of  an  annular 
intaking-  limb,  and  a  discharging-  limb  at  the  top  of  which  is 
an  annular  lip  or  mouth  piece,  the  bottom  of  which  is 
tapered  to  less  diameter.  The  discharg-ing-  limb  terminates 
in  a  weir  chamber  which  when  full  to  its  overflow  point  just 
seals  the  limb.  Over  the  crest  of  the  weir  is  a  small  syphon 
whose  function  is  to  draw  the  water  from  the  weir  chamber 
and  thus  unseal  the  syphon.  At  the  lower  end  of  the  small 
syphon  is  a  dam  or  obstruction  to  prevent  its  breaking. 
The  main  syphon  is  broug-ht  into  action  (on  the  tank  being- 
filled  i  by  means  of  a  small  stream  of  water  flowing  over  the 
annular  mouth  piece  and  falling-  free  of  the  sides  of  the  dis- 
charging- limb.  As  soon  as  the  lower  end  of  the  discharging- 
limb  has  been  sealed  by  filling-  the  weir  chamber  the  falling- 
stream  of  water  g-athers  u])  and  carries  out  with  it  a  portion 
of  the  contained  air,  thus  producing-  a  slig-ht  rarefaction. 


216 


THI-:    SEPARATE    SYSTEM    OF    SEWERAGE. 


PLATE  XX. 


r^^ffW^f^^^^^ 


ii  "^^  ■  '■^^g'^Ti^^'??^' 


riELD-WARING  FLUSH-TANK. 


This  rarefaction  causes  the  water  to  rise  in  the  intaking- 
limb  hig"her  than  in  the  basin  outside,  and  hence  increases 
the  stream  of  water  flowing-  over  the  mouth  piece,  which  in 
turn  increases  the  rarefaction,  and  the  syphon  is  soon 
broug-ht  into  full  pla}'. 

On  the  tank  being-  emptied  to  the  bottom  of  the  intaking- 
limb  the  flow  is  checked,  and  the  small  syphon  over  the 
crest  of  the  weir  draws  the  water  from  the  weir  chamber, 
air  enters  the  discharg-ing-  limb,  and  the  syphon  is  vented 
ready  for  the  tank  to  ag-ain  fill. 


PLATE  XXI. 


%"  4"  *- ' 


VLSJJJfWW\ 


:#^^^^i^^P^ai^^igSg&y' 


VAN  VRANKEN'S  FLUSH  TANK. 


CHAP,    X.  FLUSHING    AND    VKNTILATING.  219 

Van  Vranken's  Flush  Tank, — This  tank  consists  of  an 
ordinary  syphon,  to  the  ]ong-er  or  descending-  limb  of  which 
is  applied  a  small  tilting-  tank.  The  ari-angement  of  the 
parts  is  shown  in  Plate  XXI,  The  tilting  tank  is  hung 
directly  below  the  descending  limb  of  the  syphon,  at  such  a 
level  as  to  leave  its  mouth  sealed  at  all  times.  The  tilting 
basin  is  contained  in  a  small  cast  iron  chamber,  built  into  the 
bottom  of  the  flush-tank  chamber  proper.  The  action  of  the 
tank  is  as  follows: 

The  water  being  admitted  to  the  tank  by  an  ordinary 
faucet,  at  whatever  rate  may  be  desired,  gradually  rises  in 
the  tank  until  it  overflows  from  the  ascending  to  the 
descending  leg  of  the  syphon  and  is  collected  in  the  tilting 
tank.  As  it  accumulates  in  the  tilting  tank  the  center  of 
gravity  is  thrown  beyond  the  axis  of  support  and  the  pan 
tilts,  the  water  level  in  the  basin  being  lowered  about  one 
inch.  This  produces  a  corresponding  rarefaction  in  the 
syphon  and  brings  it  promptly  into  full  action.  When  the 
tank  ceases  to  discharge  the  tilting  basin  resumes  its  former 
position. 

The  Miller  Automatic  Flush  Tank.— This  flush  tank 
is  shown  in  Plates  XXII  and  XXIII,  Previous  syphons  have 
been  brought  into  action  by  the  simple  release  or  rare- 
faction of  the  air  confined  in  the  syphon,  or  by  the 
sudden  removal  of  such  air  by  special  subsidiary  devices, 
which  are  entirely  absent  in  the  "Miller"  syphon. 
It  consists  of  two  simple  Castings,  a  U  tube  or  trap 
and  mouthpiece,  cast  in  one  piece,  and  a  cast-iron  bell 
which  is  placed  over  the  longer  leg  of  the  syphon,  and  is  held 
in  place  by  brackets  cast  on  the  trap.  The  action  of  the 
syphon  is  as  follows:  As  the  water  entering  the  tank  rises 
above  the  lower  edge  of  the  bell,  it  incloses  the  air  within, 
the  lower  portion  of  the  trap  being,  of  course,  filled  with 
water.     As  the  water  level  of  the  tank  rises,  the  confined  air 


220  THE   SRPARATK   SYSTEM    OF    SEWERAGE. 

gradually  forces  the  water  out  of  the  long-  leg-  of  the  trap, 
until  a  point  is  reached  when  the  air  just  endeavors  to  escape 
around  the  lower  bend.  Now,  as  the  difference  of  water 
level  in  the  two  le^s  equals  the  difference  of  the  levels 
between  the  water  in  the  tank  and  the  water  within  the  bell, 
it  will  be  seen  that  the  column  of  water  in  the  short  dis- 
charge leg-  has  practically  the  same  depth  as  the  head  of 
water  in  the  tank  above  the  level  at  which  it  stands  in  the 
bell.  The  two  columns  of  water,  therefore,  counterbalance 
each  other  at  a  certain  fixed  depth  in  the  tank.  As  soon  as 
this  depth  is  increased  by  a  further  supply,  however  small,  a 
portion  of  the  confined  air  is  forced  around  the  lower  bend, 
and  by  its  upward  rush  carries  with  it  some  of  the  water  in 
the  short  leg-,  thus  destroying-  the  equilibrium.  But  the 
secret  of  this  invention  is  the  free  projection  of  the  overflow 
edg-e,  which  allows  of  the  instantaneous  escape  or  falling- 
away  of  the  heaved-up  water.  Thus,  if  the  discharg-e  mouth 
were  formed  as  an  ordinary  bend,  the  s3'phon  would  not  act 
(although  the  confined  air  rushes  around  the  lower  bend), 
for  the  simple  reason  that  the  heaved-up  water  has  no  means 
of  instantaneous  escape,  and,  therefore,  the  equilibrium  is 
not  sufficiently  disturbed.  It  will  thus  be  seen  that  the 
action  of  the  syphon  depends,  not  on  the  escape  of  air,  but  on 
the  sudden  reduction  of  a  counterbalancing-  column  of  water. 
Repeated  trials  have  shown  that  a  6-inch  syphon  will 
discharg-e  full  bore  a  500-g-allon  tank,  fed  so  slowly  as  only  to 
be  filled  in  fourteen  days.  There  being-  no  internal  obstruc- 
tion, the  discharg-e  is  extremely  rapid. 

Rhoads-Williams  Flush-Tank.— The  Rhoads-Williams 
syphon,  as  illustrated,  consists  of  an  annular  intaking  limb, 
and  a  discharg-ing-  limb  terminating-  in  a  deep  trap  below  the 
level  of  the  sewer.  Below  the  permanent  water  line  in  the 
discharging-  limb,  is  connected  one  end  of  a  small  blow-off  or 
relief-trap,  having-  a  less  depth  of  seal  than  the   main   trap. 


PLATE  XXII 


THE  MILLER    AUTOMATIC   FLUSH  TANK. 


PLATE  XXIII. 


THE  MILLER  AUTOMATIC  PUSH   TANK, 
Combined  with  Manhole. 


CHAP.    X.  FLUSHING    AND    VliNTH.ATING.  225 

the  other  end  of  which  joins  the  main  trap  on  the  opposite 
side,  at  its  entrance  to  the  sewer  and  above  the  water  line  of 
the  trap.  At  the  same  point  is  connected  an  uprig-ht  vent 
pipe  which  rises  throug-h  the  tank  to  a  point  above  the  hig-h 
water  line,  and  is  turned  down  throug-h  the  top  of,  and  into 
the  intaking-  limb  of  the  syphon,  terminating-  at  a  g-iven  point 
above  its  bottom. 

As  the  tank  fills  with  water  (the  main  and  blow-off  traps 
being-  full)  it  rises  in  the  intaking-  limb  even  with  the  level  of 
the  water  in  the  tank  until  reaching-  the  end  of  the  vent  pipe, 
a  volume  of  air  is  confined  in  the  two  limbs  of  the  syphon 
between  the  water  in  the  intaking-  limb  and  the  water  in  the 
main  trap.  As  the  water  rises  higher  in  the  tank  the  con- 
fined volume  of  air  is  compressed  and  the  water  is  depressed 
in  the  main  trap  and  in  the  blow-off  trap.  This  process 
g-oes  on  until  the  water  in  the  tank  reaches  its  hig-hest  level 
above  the  top  of  the  intaking-  limb  at  which  time  the  water  is 
depressed  in  the  blow-off  trap  to  the  lowest  point  and  the 
confined  air  breaks  throug-h  the  seal,  carrying  the  water 
with  it  out  of  the  trap,  thus  releasing-  the  confined  air  and 
allowing-  an  inflow  from  the  tank,  putting-  the  syphon  into 
operation. 

On  the  tank  being-  discharged  to  the  bottom  of  the  intak- 
ing limb,  the  flow  is  checked  and  the  syphon  is  vented  by  the 
admission  of  air  to  it  throug-h  the  vent  pipe. 

The  Lightning  Automatic  Flush-Tank. — The  operation 
of  this  flush-tank  is  as  follows:  See  Plate  XXV. 

The  water  rises  in  the  tank  till  it  reaches  the  float  "F" 
of  the  lever,  it  also  rises  under  the  air  chamber,  but  owing- 
to  compression  of  the  contained  air  the  water  will  rise  only 
to  within  one  inch  below  the  top  of  the  inner  leg- at  the  time 
its  outer  level  will  have  reached  the  center  of  the  float  in  the 
tank.  The  rising-  water  acting  on  the  float  "F"  then  moves 
the  lever  "H"  which   holds  down  the  hing-ed  chamber  "I." 


226 


THE    SEPARATE   SYSTEM    OF    SEWERAGE, 


PLATE  XXIV. 


FTfSr^T3T^7?p^3" 


RHOADS-WILLIAMS   FLUSH-TANK. 


The  instant  the  lever  moves  and  releases  the  chamber  the 
latter  springs  open  on  its  hing-es  and  the  inner  confined  air 
bodily  escapes.  Gravity  bring-s  the  chamber  back  to  its 
orig-inal  position  immediately  that  the  air  has  escaped,  and 
full  and  complete  syphonag-e  takes  place. 

Valve  Tanks. — In  the  valve  tanks  the  valve  is  usually 
operated  by  a  float  which  releases  the  valve  when  the  water 
has  reached  a  certain  level. 


PLATE  XXV. 


THE 

LIGHTNING 

AUTOMATIC 

FLUSH-TANK 


CHAP.   X.  FLUSHING    AND    YPZNTILATINC.  229 

Requirements  to  be  Met. — The  requisites  for  an  auto- 
matic flush-tank  are:  1,  Certainty  of  action;  2,  rapidity  of 
discharg-e;  3,  simplicity  of  construction;  4,  ease  of  inspec- 
tion of  all  its  parts;  5,  durability;  6,  economy  of  cost  and 
maintenance. 

Strang-e  as  it  may  appear,  there  are  flush-tank  syphons, 
sold  in  considerable  numbers,  which  cannot  possibly  be 
made  to  work  under  the  usual  conditions  imposed  b}'  the 
requirements  for  flushing-  sewers. 

Rapidity  of  discharg-e  is  next  in  importance  to  certainty 
of  action.  The  sewer  pipe  should  be  filled  for  some  distance 
in  order  to  g-et  the  proper  benefit  from  the  flush. 

In  simplicity  of  construction  the  syphon  tanks  are  supe- 
rior to  the  valve  tanks,  and  as  durability  is  likely  to  depend 
upon  simplicity  of  construction,  the  syphon  tanks  will,  in 
g-eneral,  be  most  durable. 

Complicated  mechanism  is  undesirable  for  use  in  a 
flush-tank,  which  must  work  automaticall}',  and  often  for  a 
long-  time  without  inspection.  It  is  not  at  all  uncommon  to 
find  that  devices  which  look  well  on  paper  fail  utterly  when 
put  to  the  test  of  actual  service. 

Quantity  of  ^A^ater  Required. — An  erroneous  idea  pre- 
vails as  to  the  quantity  of  water  required  for  flushing-  sewers 
bv  the  use  of  automatic  flush  tanks.  A  properly  desig-ned 
system  for  a  city  of  10,000  inhabitants  ordinarily  requires 
from  twenty  to  fifty  flush-tanks,  of  a  capacity  of  about  150  to 
300  g-allons,  discharg-ing-  daily,  or  at  most  twice  a  day.  The 
maximum  amount  of  water  required  is  about  two  per  cent, 
of  the  water  supply.  This  momentary  discharg-e  does  not 
sensibly  occupy  the  capacity  of  the  main  sewers  further 
down  the  line,  being-,  as  before  stated,  but  a  ver}'  small  per- 
centag-e  of  the  ultimate  discharg-e.  An  equally  efficient 
flushing-  by  a  constant  stream,  applied  directly  and  without 
the  intervention  of  a  flush  tank  would  require  an  amount  of 


230  THE   SEPARATK   SYSTEM    OF    SEWfc:RAGE. 

water  materially  encroaching-  upon  the  capacity  of  the  main 
sewers,  and  would  be  inadmissible  under  ordinary  condi- 
tions of  water  supply,  on  the  score  of  economy. 

Rapidity  of  Discharge. — Flush-tanks  are  ordinarily 
adjusted  to  discharg-e  automatically  once  in  each  twenty-four 
hours.  Their  capacity  of  discharg-e  should  equal  or  exceed 
that  of  the  pipe  into  which  they  empty. 

Experiments  made  by  the  writer  with  a  flush-tank  of 
7,000  g-al Ions  capacity,  having-  a  ten-inch  outlet,  opening-  into 
an  eig-ht-inch  sewer,  demonstrated  that  with  the  minimum 
grades  indicated  in  Table  XV,  there  was  no  dang-er  of  g-org-- 
ing-  the  sew^er  at  a  distance  of  one  or  two  hundred  feet  from 
the  flush-tank,  althoug-h  the  hydraulic  head  was  seven  feet 
and  the  capacity  of  the  tank  was  sufficient  to  fill  the  sewer 
for  a  distance  of  2,682  feet.  At  a  distance  of  600  feet  the 
flow,  as  observed  in  a  man-hole,  did  not  fill  the  sewer. 

In  the  case  of  flush  tanks  as  ordinarily  constructed  the 
tank  can  hardly  discharg-e  too  rapidly. 

The  rate  of  discharg-e  from  the  tank  should  at  least 
equal  the  capacity  of  the  sewer  when  the  flow  has  acquired 
the  velocity  due  to  its  inclination.  A  sewer  six  inches  in 
diameter,  laid  at  a  g-rade  of  five-tenths  per  hundred,  dis- 
charg-es,  when  full,  at  the  rate  of  215  g-allons  per  minute. 
The  conditions  above  named  would  therefore  require  the 
tank  to  discharg-e  at  the  rate  of  100  g-allons  in  28  seconds  or 
less. 

Experimental  Data.^Some  valuable  experiments  were 
made  upon  the  effect  of  flush  tanks  in  the  sewers  in  Wash- 
ing-ton, D.  C,  by  Asa  E.  Phillips,  Assistant  Eng-ineer,  Dis- 
trict of  Columbia,  and  the  results  were  presented  by  him  in 
a  paper  read  before  the  American  Society  Municipal 
Improvements,  in  October,  1898. 


CHAP.   X.  FLUSHING    AND    VICNTILATING.  231 

The  following-  extracts  are  taken  from  his  paper: 

"No  formula  has  been  proposed  for  the  volume  of  water  required  for  dif- 
ferent grades  and  sizes,  and  the  only  rule  known  to  have  been  used  appears  to 
be  of  little  value.  This  important  detail  is  determined  by  individual  judgment, 
generally  unsupported  by  investigation  or  experience,  so  that  the  common 
practice  has  varied  within  a  large  range  of  values,  while  tanks  of  uniform  size 
usually  have  been  constructed  regardless  of  differences  in  the  size  or  gradient 
of  the  sewers  to  be  flushed.  The  uncertainty  as  to  the  precise  effect  of  the 
flush  and  the  complex  conditions  as  to  contributing  population,  rate  of  water 
consumption,  etc.,  have  been  justly  considered  a  bar  to  any  precision  in  this 
respect  Recent  discussion  of  the  subject,  however,  has  tended  to  establish 
certain  limitations  in  the  use  of  flushing  devices  which  should  lead  to  improve- 
ment in  the  general  practice. 

"The  work  to  be  accomplished  by  the  flush  is  the  removal  at  regular  and 
frequent  intervals  of  solid  matter  flushed  into  the  sewer  from  house  laterals, 
and  there  stranded  because  of  the  shallow  depth  of  flow  and  sluggish  current 
and  its  carriage  down  the  line  to  a  point  where  the  depth  and  velocity  are 
sufiScient  to  insure  removal  to  the  ultimate  point  of  discharge.  The  efficiency 
of  the  flushing  device  in  performing  this  work  is  not  well  understood.  But 
little  is  known  of  the  effect  under  the  varying  conditions  encountered,  espe- 
cially for  widely  different  grades  and  at  considerable  distance  from  the  dead 
end.  It  is  generally  considered,  however,  that  the  effect  diminishes  very 
rapidly  as  the  distance  increases,  and  becomes  almost  imperceptible  600  or  700 
feet  from  the  tank,  but,  so  far  as  can  be  ascertained,  this  has  been  observed 
only  in  cases  of  flush  of  small  volume  on  flat  grades,  or  where  the  depth  of 
ordinary  flow  was  considerable.  Of  the  effect  of  discharge  of  600  gallons  or 
more,  such  as  were  used  in  the  cases  to  follow,  there  appears  to  be  no  recorded 
observations,  so  that  no  comparison  with  those  already  published  can  be  made. 
Several  grade  conditions  have  been  selected  for  the  purpose  of  illustrating  the 
effect  of  the  flush  under  such  circumstances,  and  an  attempt  made  to  indicate 
by  means  of  diagrams  the  different  results  obtained.  For  these  no  special 
accuracy  is  claimed,  but  in  the  few  cases  given  the  differences  are  sufficiently 
marked  as  to  suggest  certain  conclusions  therefrom. 

"The  Park  street  line  is  the  first  of  these.  This  sewer  is  12  inches  in 
diameter,  about  1,870  feet  in  length,  and  has  a  uniform  grade  throughout  of  9 
inches  per  ico  feet.  Preliminary  examination  discovered  slightly  unfavorable 
conditions  for  experimental  work,  such  as  an  uneven  grade,  rough  joints,  and 
poor  alignment  in  places,  all  of  which  affected  the  observations  and  results  to 
some  extent.  It  may  now  be  stated  that,  with  the  exception  of  the  Chapin 
street  line,  the  sewers  cited  are  old  and  generally  possess  these  irregularities, 
but,  excepting  slight  silt  accumulation  at  points  distant  from  the  basin,  they 
were  found  to  be  very  clean.     The  presence  of  even  a  small  amount  of  silt  in 


232 


THE    SEPARATE   SYSTEM    OF    SEWERAGE. 


the  invert,  particularly  at  man-holes,  undoubtedly  affected  the  flow  and  was 
the  chief  source  of  error  in  the  observations 

"The  tank  on  Park  street  was  found  to  have  an  effective  capacity  of  84 
cubic  feet,  or  about  630  gallons,  and  discharged  through  an  8-inch  syphon  in 
the  mean  time  of  forty-two  seconds.  No  attempt  was  made  to  determine  the 
velocity  at  the  point  of  discharge,  but  this  data  would  indicate  an  approximate 
mean  velocity  of  6  feet  per  second.  Observations  of  the  flush  were  simulta- 
neously taken  at  all  of  the  man-holes,  and  the  depths  of  flow  were  recorded  at 
intervals  of  fifteen  seconds  or  less.  These  depths  were  referred  to  the  time  of 
syphon  discharge,  and  the  diagrams  of  the  flush  have  been  constructed  from 
this  datum. 

"The  first  diagram,  (Fig.  i,  Plate  XXVI),  shows  the  form  of  the  flush  wave 
as  taken  at  five  consecutive  man-holes  within  1000  feet  of  the  tank.  The  lower 
four  man-holes  were  not  platted  because  of  the  confusion  of  lines  that  would 
result,  but  the  data  are  given  in  Table  XXII.  This  diagram  and  tabulation 
show  how  well  the  depth  of  flow  is  maintained  for  very  long  distances.  One 
thousand  feet  from  the  dead  end  the  flush  is  very  efficient,  and  at  a  distance  of 
nearly  2,000  feet  appears  to  be  quite  effective.  This  large  radius  of  effect  is 
doubtless  due  to  the  volume  of  water  used,  as  published  data  for  smaller  dis- 
charges indicate  that  a  tank  of  half  this  capacity  would  have  a  very  greatly 
diminished  influence. 


TABLE  XXII.— F,irk  Street  Se'oer. 

CAPACITY  OF  TANK,    84  CUBIC  FEET=630  GAL.;    TIME  OF  DISCHARGE,    42  SEC. 


Manhole. 

Size 
(Diameter). 

Gradient. 

Distance 

from 
dead  end. 

Depth  of  Flow. 

Duration 

of  greatest 

effect. 

Normal. 

Flush. 

I 
2 
3 
4 
5 
6 

7 
8 

9 
10 

Inches. 
12 
12 
12 
12 
12 
12 
12 
12 
12 
12 

Per 

0 

cent . 
75 
75 
75 
75 
75 
75 
75 
75 
75 
75 

FecH. 

200 

382 

572 

738 

948 

1,132 

i>332 

1,486 

1,688 

1,869 

Inches. 

H 
% 

I 

Inches. 
7% 

sYa 

5 

Min.    Sec. 
I      00 

I      15 

1  45 

2  00 

2      15 

1^4 

4 

y/z 
3 '4 

2  50 

3  00 
3     45 
3     45 

"The  second  diagram  for  this  line,  (Fig.  2,  Plate  XXVI),  shows  the  com- 
puted velocity  curve  for  the  ordinary  flow,  the  assumed  velocity  to  prevent  sed- 
imentation and  the  accelerated  velocitv  due  to  the  flush.     These  curves  are  not 


CHAP.  X. 


FLUSHING    AND    VENTILATING. 


233 


supposed  to  be  precise,  but  they  illustrate  the  purpose  of  the  flushing  device, 
and  to  some  extent  the  degrees  of  effectiveness  required.  The  curve  of  normal 
flow  shows  the  very  low  velocity  along  the  upper  portion  of  the  line,  and  its 
gradual  increase  approaching  the  required  velocity  at  the  lower  end,  while  the 
flush  curve  shows  a  corresponding  high  velocity  at  the  upper  end  and  its  rate 
of  fall  toward  the  2J^-foot-per-second  velocity,  where  in  theory  at  least  it 
would  seem  that  the  two  curves  meet  at  a  common  tangent  point.  In  this 
sewer,  it  may  be  noted,  the  normal  flow  does  not  attain  a  rate  of  2^  feet  per 
second,  and  probably  would  not  for  a  distance  of  2,000  feet.  It  is  also  to  be 
observed,  however,  that  the  flush  would  seem  to  maintain  this  velocity  for  a 
distance  probably  as  great;  so  that,  so  far  as  these  observations  go,  they  indi- 
cate that  for  this  very  long  line  and  flat  grade  the  flush  tank  is  efiBcient  and  of 
the  proper  size. 

"The  second  series,  taken  on  one  of  the  Connecticut  avenue  sewers,  is 
chiefly  interesting  as  showing  the  effect  produced  on  a  varying  and  decreasing 
gradient. 

TABLE  XXni.—Connec/icitt  .47'e?iue  Sc-u-er. 

CAPACITY  OF  TANK,    S2   CUBIC  FEET=6l5  GAL.;    TIME  OF   DISCHARGE,    45   SEC. 


Manhole. 

Size 
(Diameter). 

Grade. 

Distance 

from 
dead  end. 

Depth  of  Flow. 

Duration 

of  greatest 

effect. 

Normal. 

Flush. 

I 
2 

3 
4 

Inches. 
12 
12 
12 
12 

Per  cent. 

I 
I 
0.4 

I 

Feet 
175 
325 
473 
613 

Inches. 

-A 

I 

Inches. 
5'A 
5% 
5% 
3% 

Min.    Sec 
I      15 
I      30 
3     00 
3     00 

"The  diagram,  (Fig.  3,  Plate  XXVI),  illustrates  the  diminished  velocity  and 
enlarged  area  of  section  of  the  flush  wave,  as  recorded  at  man-hole  No.  3, 
showing  the  marked  effect  of  the  diminished  rate  of  grade  in  the  portion  of  the 
sewer  immediately  above.  Unfortunately  this  could  not  be  further  observed, 
owing  to  a  change  in  gradient  from  this  point.  It  probably  indicates,  however, 
that  for  a  line  of  varying  slope  the  minimum  should  be  considered  in  fixing  the 
capacity  of  the  tank. 

"The  third  series  was  taken  on  the  Chapin  street  sewer,  which  has  the 
reversed  conditions  of  a  varying  but  rapidly  increasing  gradient.  The  observed 
effect  of  the  flush  is  very  clearly  shown  by  the  diagram,  (Fig.  4,  Plate  XXVI). 
The  rapid  run-off  and  greatly  reduced  area  of  section  toward  the  lower  end  of 
the  sewer  indicate  the  very  high  velocity  which  such  steep  slopes  must  produce. 
In  this  case  the  minimum  grade  being  i  per  cent.,   and  that  for  a  length  of  only 


234 


THE    SEPARATE   SYSTEM    OF    SEWERAGP:. 


190  feet,  a  flush  tank  of  considerably  less  capacity  would  probably  be  suffi- 
ciently effective,  if,  indeed,  for  such  grade  conditions  automatic  flushing  is  at 
all  necessary. 

TABLE   XXIV.  — «.///«  S/reel  Sewer. 

CAPACITY  OF  TANK  83  CUBIC  FEET^620  GAL.;    TIME  OF  DISCHARGE,    48  SEC. 


Manhole. 

Size 
(Diameter). 

Grade. 

Distance 

from 
dead  end. 

Depth  of  Flow. 

Duration 

of  greatest 

effect. 

Normal. 

Flush. 

I 
2 

3 
4 

Inches. 
12 
12 
12 
12 

Per  cent. 
I 
2 

5-6 
9 

Feel. 
190 
350 
490 
705 

Inches. 

Inches. 
3 

M/n.    Sec. 
I      00 
I      00 
I      00 
I      00 

"The  fourth  series,  taken  on  one  of  the  Thirty-second  street  sewers,  shows 
the  observed  effects  on  a  nearly  uniform  steep  grade.  The  first  diagram,  (Fig. 
5,  Plate  XXVI),  for  this  line  shows  the  form  of  the  flush  wave  as  observ.ed  at 
each  manhole.  The  quick  run-off  and  nearly  uniform  area  of  section  main- 
tained indicate  the  piston-like  effect  of  the  discharge.  In  fact,  the  flow  was  so 
rapid  and  so  quickly  past  as  to  render  the  taking  of  the  observations  rather 
difficult  and  their  relative  accuracy  to  some  degree  uncertain. 

TABLE   XXV.—  Thir/r-Secom/  Street  Sewer. 

CAPACITY  OF  TANK,    84  CUBIC  FEET=63Q  GAL.;    TIME  OF  DISCHARGE,    48  SEC. 


"The  curves  here  and  there  seem  to  suggest  such  unavoidable  irregulari- 
ties, but  the  general  effect  is  very  clearly  shown.  The  second  diagram,  (Fig. 
6,    Plate  XXVI),    indicates  the  appro.ximate  velocity  attained  by   the  flush  in 


•S3L|DU|  Ul  MOlJ   p  mdSG 


CHAP.   X.  FLUSHING    AND    VKNTILATING.  237 

connection  with  the  assumed  2^  feet  per  second  constant,  as  well  as  the  esti- 
mated velocity  of  ordinary  flow.  This  shows  in  another  form  the  marked 
effect  of  the  discharge  on  a  steep  slope,  and  also  how  quickly  on  such  grades 
the  normal  flow  attains  sufficient  velocity  to  prevent  deposit.  From  a  study  of 
these  diagrams  we  may  conclude  that  the  flush  increases  rapidly  in  effective- 
ness as  the  grade  increases,  having  a  remarkable  scouring  power  on  grades  of 
4  per  cent,  or  more,  but  at  the  same  time  the  necessity  of  automatic  flushing 
decreases  correspondingly,  there  being  apparently  little  need  for  such  a  device 
on  slopes  approaching  4  per  cent." 

"As  has  been  seen,  no  attempt  is  here  made  to  indicate  the  results  with  a 
variable  volume  of  discharge  for  the  purpose  of  determining  the  comparative 
radius  of  effect  under  such  circumstances.  This  and  other  interesting  details 
are  necessarily  omitted,  an  effort  having  been  made  only  to  show  the  general 
influence  of  the  slope  on  the  flush,  and,  in  a  limited  way,  the  range  of  efi'ect." 

Some  valuable  data  on  the  effectiveness  of  flush-tanks 
has  also  been  secured  by  Mr.  H.  N.  Og"den  from  experi- 
ments at  Ithica,  N.  Y.,  a  record  of  which  appears  in  the 
Transactions  of  the  American  Society  of  Civi'l  Eng-ineers, 
December,  1898. 

Plate  XXVII  is  reproduced  from  Mr.  Fuertes  discussion 
of  the  data  in  the  Transactions  and  the  following  extract  is 
also  from  his  discussion: 

"On  the  diagram,  Plate  XXVII,  is  shown  the  form  of  the  flushing  wave  dis- 
charged into  the  Green  street  sewer,  drawn  from  the  author's  data.  A  profile 
of  the  wave  is  shown  at  the  end  of  the  ist,  2nd,  3rd,  4th,  6th,  8th  and  loth 
minutes.  In  this  diagram  the  shapes  of  the  waves  are  not  claimed  to  be  exact 
as  to  profile  at  all  points.  They  are  accurate  at  the  points  where  they  cross 
the  man-holes,  and  the  positions  of  the  toes  of  the  waves  were  interpolated; 
the  remaining  portions  of  the  curves  are  sketched  in. 

"The  velocities  corresponding  to  the  greatest  depths  of  flow  were  calcu- 
lated by  the  Kutter  formula,  (n==o.oi3).  The  velocities  marked  for  the  toe  of 
the  wave  are  the  components,  along  the  bottom  of  the  sewer,  of  the  velocities 
of  the  surface  of  the  water  at  the  given  points  when  the  wave  reaches  those 
points. 

"At  the  first  man-hole  the  sewer  was  nearly  full,  and  probably  had  been 
running  under  a  head  up  to  within  about  60  feet  of  the  man-hole.  After  pass- 
ing this  point  the  foot  of  the  descending  body  of  water,  under  a  free  flow  by 
gravity,  rushed  forward  rapidly,  the  point  being  135  ft.,  265  ft.,  391  ft.,  513  ft., 
630  ft.,  743  ft.,  852  ft.,  and  957  ft.  distant  from  the  man-hole  in  i,  2,  3,  4,  5,  6, 


238 


THE    SEPARATE    SYSTEM  OF    SEWERAGP:. 


7  and  8  minutes,  respectively.  Traversing  these  distances  in  the  times  given 
corresponds  to  an  average  velocity  between  the  respective  points  of  2.25  ft., 
2.18  ft.,  2  10  ft.,  2.03  ft.,  1.95  ft.,  i.8g  ft.,  1.81ft.  and  1.75  ft.  per  second. 
These  are  the  bottom  velocities  at  the  point  of  the  wave,  and  are  the  actual 
maximum  velocities  at  the  respective  points." 


■«3«3S  JO  3d01S  UOi  i33J  JO  31VDSJ 


General  Statements. — From  the  observed  facts  above 
quoted,  and  also  from  the  theory  of  hydraulics,  the  following- 
general  statements  concerning-  the  efficiency  of  flushing  may 
be  made: 


CHAP.  X.  FLUSHING    AND    VENTILATING.  239 

The  efficiency  of  flush  is  proportional  to 

(1)  The  velocity  of  flow; 

(2)  The  depth  of  flow; 

(3)  The  duration  of  flow. 

The  velocity  of  flow  is  proportional  to  the  rate  of  dis- 
charg-e  and  the  inclination  of  the  sewer.  (We  are  now  con- 
sidering- sewers  of  a  g"iven  diameter.)  The  inclination  being- 
fixed  and  uniform  the  velocity  is  ordinarily  less  as  the  dis- 
tance from  the  flush  tank  increases. 

The  depth  of  flow  is  proportional  to  the  rate  of  dis- 
charg-e  and  (under  the  conditions  usual  in  sewers)  inversely 
proportional  to  the  inclination  of  the  sewer.  The  rate  of 
discharg-e  being-  fixed  and  the  inclination  being-  fixed  and 
uniform  it  is  usually  less  as  the  distance  from  the  flush-tank 
increases. 

The  duration  of  flow  is  proportional  to  the  quantity  and 
rate  of  discharge  and  inversely  proportional  to  the  inclina- 
tion of  the  sewer.  Under  the  usual  conditions  of  quantity, 
rate  and  inclination,  the  duration  of  flow  is  g-reatest  at  points 
farthest  from  the  flush  tank.  This  naturally  follows  from 
the  fact  that  the  wave  crest  becomes  lower  and  the  velocity 
less  as  the  distance  from  the  tank  increases  as  illustrated  in 
the  diag-rams. 

The  velocity  and  depth  of  flow  are  interdependent. 
Depth  of  flow  is  particularly  advantag-eous  as  it  induces 
velocity.  Depth  of  flow  is  desirable,  however,  independent 
of  its  influence  on  velocity  since  it  increases  the  cleansing- 
contact  at  the  sides  of  the  sewer,  increases  the  section  of 
stranded  matters  which  are  exposed  to  the  current,  and,  by 
a  g-reater  degree  of  immersion  makes  their  hold  upon  the 
invert  of  the  sewer  less  stable. 


CHAPTER  XI. 

HOUSE  DRAINAGE  AND  PLUMBING. 

House  Connections. — In  order  to  protect  the  sewers 
from  injury  b}^  careless  or  incompetent  workmen,  or  from 
stoppag-e  by  the  introduction  of  improper  substances  into 
the  sewers,  proper  rules  and  reg"ulations  for  house  drains 
and  connections  are  necessary. 

To  permit  each  householder  to  connect  with  the  sewers 
whatever  he  chooses,  wherever  he  chooses  and  in  whatever 
way  he  chooses,  is  to  insure  ruin  to  the  whole  system.  The 
house  drains  should  be  connected  only  at  the  Y's,  which 
have  been  placed  in  position  when  constructing-  the  sewers. 

All  work  should  be  done  by  competent  workmen,  who 
are  under  bonds  to  do  the  work  properly  and  repair  all  dam- 
ag"e  they  may  do,  and  under  the  direction  of  a  trustworthy 
eng-ineer  or  inspector. 

Care  must  be  taken  to  exclude  everything*  which  will  be 
liable  to  obstruct  the  sewers.  The  man  who  said  that  he 
thoug"ht  "the  sewers  should  carry  potato  peeling's  and  such 
thing-s"  is  not  alone  in  his  notions  reg^arding^  the  disposal  of 
g"arbage.  A  larg^e  majority  of  the  domestics  employed  in 
families  have  unlimited  faith  in  the  capacity  of  waste  pipes 
and  sewers  to  carry  empty  cans,  broken  bottles,  ashes,  cin- 
ders, wash  cloths,  etc.  This  confidence  in  the  carrying- 
power  of  a  pipe  is  so  firm  that  it  will  be  found  easier  to  ren- 
der the  introduction  of  miscellaneous  articles  impossible 
than  to  demonstrate  that  the  transportation  qualities  of  a 
sewer  are  limited.  It  will  be  much  better  to  prevent 
improper  thing-s  being-  introduced  into  the  sewers  than  to  be 
oblig-ed  to  dig-  up  the  pipes  to  remove  obstructions.  The 
sewers  are  intended  to  carry  only  fluid  refuse  from  kitchens, 


CHAP.    XI.  HOUSK    DRAINAGE    AND    PLUMBING.  241 

laundries,  water  closets,  bath-tubs,  slop  sinks,  etc.,  and  care 
must  be  taken  to  exclude  all  solids,  cloths,  mud  and  an}'- 
thing"  which  would  be  liable  to  obstruct  the  flow  in  the  pipes. 
The  house  drains  will  be  much  more  likely  to  g^et  into 
bad  condition  than  the  public  sewers,  and  hence  the  neces- 
sity for  g"reat  care  in  laying-  the  drain  and  in  providing-  for 
its  ventilation  and  flushing-. 

Municipal  Control. — It  will  be  found  best  to  pass  a  g-en- 
eral  ordinance  g-overning-  the  use  of  sewers  by  private  indi- 
viduals. 

The  following-  forms  thoug-h  not  universally  applicable 
may  be  useful  as  g-uides  in  outlining  work  of  this  kind. 

ORDINANCE. 

An  Ordinance   Fixing  and   Regulating   the   Use   of    Sewers   by  Private 
Individuals  in  the  City   of 

Section  i.     The  Sanitary  Sewer  system  of  the  city  of 

consists  of 

Main  and  lateral  conduits  of  salt-glazed,  vitrified  earthen-ware  or  brick, 
with  necessary  accessories.  They  are  designed  to  carry  off  all  liquid  house 
wastes,  and  are  known  herein  as  sanitary  sewers.  The  sewers  in  the  streets 
passing  in  front  of  the  various  lots  are  called  main  or  lateral  sewers.  The 
sewers  leading  from  the  main  or  lateral  sewers  to  the  property  on  either  side 
are  called  house  sewers.  Porous  drains  laid  for  removing  subsurface  water  are 
called  subsoil  drains. 

connections. 

Sec   2*      All  connections  of  house  sewers,   drains  or  plumbing  work  with 

the  sewer  system  of  the  city  of shall  be  made  in  accordance  with 

these  rules  and  regulations. 

licensed   plumbers. 

Sec  3.  No  person,  firm  or  corporation  shall  lay,  alter  or  repair  any 
house-drain,  sewer  or  plumbing  work  or  make  any  connections  whatever  with 
any  sewer  or  drain  belonging  to  the  sanitary  sewer  system,  or  do  any  kind  of 
work  connected  with  the  laying  of  house-drains  or  house-sewers  or  plumbing  or 
making  any  repairs,  additions  to  or  alterations  of  any  drain,   sewer  or  plumb- 


242  THK    SliPAKATE    SYSTEM    OF    SEWERAGE. 

ing  connected,  or  designed  to  be  connected  with  the  sanitary  sewer  system, 
unless  regularly  licensed  by  the 

APPLICATION    FOR    LICENSE. 

Sec   4.     Any  person  desiring  to  do  business  as  a  plumber,  in  connection 

with  the  sanitary  sewer  system,  shall  file  in  the  ofifice  of  the 

a  petition  giving  the  name  of  the  individual  or  firm  and  place  of  business,  and 
asking   to  be   licensed   as  a  plumber.       Said  petition  must  be  signed  by  two 

responsible  citizens,  of  the  city  of vouching 

for    the    business    capacity   and    reputation   of    the   applicant — that    he    is    a 

resident  of a  master  of  his  trade,  and 

willing    to    be   governed    in    all    respects    by  the  rules  and  regulations    which 

are  or  may  be  adopted  by  the Each  applicant  for  a  license 

shall  e.vecute  and  deposit  in  the  office  of  the with  his  appli- 
cation,  a  bond  with  two  or  more    resident    sureties,    to  be  approved  by  said 

in  the  sum  of conditioned 

that  he  will  indemnify  and  save  harmless  the  city  of , ...    from 

all  accidents  and  damages  caused  by  any  negligence  in  protecting  his  work,  or 
by  any  unfaithful,  imperfect  or  inadequate  work  done  by  virtue  of  his  license, 
and  that  he  will  also  replace  and  restore  sidewalk,  pavement  or  street  surface 
over  any  opening  he  may  have  made  to  as  good  state  and  condition  as  he  found 
it,   and  keep  and  maintain  the  same  in  good  order,   to  the  satisfaction  of  the 

for  the  period  of  six  months  next  thereafter,  and  that 

he  will  pay  all  fines  imposed  upon  him  for  a  violation  of  any  of  these  rules  or 
regulations.     On  receiving  his  license  he  shall  have  recorded  in  the  office  of  the 

his  actual  place  of  business,    the  name  under  which  the 

business  is  transacted,  and  shall  immediately  notify  the of  any 

change  in  either  thereafter.      No  license  will  be  granted  for  more  than  one 

year  and  all  licenses  will  be  granted  to  expire  on  the day  of 

Removal  of  residence  from  the  city  shall  act  as  a  forfeiture  of  license. 

PERMITS. 

Sec.  5.  Applications  for  permits  to  connect  with  the  sewer  system  or  do 
plumbing  work  to  be  connected  therewith,  must  be  made  in  writing  by  the 
owner  of  the  property  to  be  drained  or  his  authorized  agent.  Such  applica- 
tion shall  give  the  precise  location  of  the  property,  the  name  of  the  owner  and 
the  name  of  the  person  employed  to  do  the  work,  and  shall  be  made  on  blanks 
furnished  for  the  purpose.  No  permit  shall  be  deemed  to  authorize  anything 
not  stated  in  the  application,  and  for  any  misrepresentation  in  such  applica- 
tion the  plumber  shall  be  suspended;  and  if  such  misrepresentation  appears  to 
be  wilful  his  license  shall  be  revoked. 

Permits  to  make  connection  with  the  sewer  system  will  be  issued  onh- 
when  the  plumbing  in  the  house  or  building  to  be  connected  is  in  accordance 


CHAP.  XI.  nousi';  drainage  and  plumbing.  243 

with  the  rules  for  plumbing  hereinafter  prescribed  and  has  been  inspected 
and  approved  by  the  Superintendent  of  Sewers,  or  in  case  of  new  buildings 
when  a  proper  plan  for  the  plumbing  has  been  approved  by  the  Superintendent. 
The  Superintendent  will  designate  the  position  of  the  "Y"  branch  in  the 
street,  as  shown  by  the  records  in  the office.  All  con- 
nections made  with  the  sanitary  sewers  or  drains  and  all  plumbing  connecting 
therewith  shall  be  made  under  the  direction  of  the  Superintendent  of  Sewers 

PLAN    OF    PLUMBING. 

Sec.  6.  Before  a  permit  will  be  issued  for  doing  plumbing  work  in  a 
building,  or  before  any  additions  are  made,  excepting  necessary  repairs,  a  plan 
and  description  of  the  work  to  be  done  signed  by  a  licensed  plumber  on  blanks 
furnished  for  the  purpose  shall  be  filed  in  the  office  of  the  sewer  department, 
and  no  such  work  shall  be  commenced  until  such  plan  shall  have  been 
approved  by  the  Superintendent. 

Every  plan  shall  cotjtain  a  clear  and  full  description  of  the  plumbing, 
showing  the  position,  size,  kind  and  weight  of  all  pipes,  and  the  position  and 
kind  of  traps,  closets  and  other  fixtures.  All  work  done  under  such  plans  shall 
be  subject  to  the  inspection  of  the  Superintendent,  and  no  alteration  shall  be 
made  in  any  plan  or  in  the  work  without  a  special  permit  in  writing  from  him. 

INSPECTION. 

Sec.  7.  The  Superintendent  is  to  be  given  notice  when  any  work  is 
ready  for  inspection,  and  all  work  must  be  left  uncovered  and  convenient  for 
examination  until  inspected  and  approved.  Such  inspection  shall  be  made 
within  twenty-four  hours  after  such  notification.  The  Superintendent  may 
apply  the  ether,  peppermint,  water  or  smoke  test,  and  the  plumber  shall  fur- 
nish all  necessary  tools,  labor  and  assistants  for  such  tests.  The  plumber  shall 
remove  or  repair  any  defective  material  or  labor  when  so  ordered  by  the 
Superintendents 

STATEMENT    OF    WORK    DONE. 

Sec  8.  The  plumber  shall,  on  the  completion  of  the  work,  file  in  the 
office  of  the  Sewer  Department,  on  blanks  furnished  for  the  purpose,  a  correct 
statement  of  the  work  done  under  the  permit. 

CESS-POOLS — OVER-FLOWS. 

Sec.  9.  No  open  gutter,  cess-pool  or  privy  vault  shall  be  connected  with 
any  sewer  or  drain.  Cellar  and  cistern  over-flows  may  be  connected  with  the 
sewer  or  drain  only  when  they  can  be  trapped  in  such  a  manner  that  the  water 
seal  cannot  be  destroyed. 


244  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 


INJURY    TO    SEWERS. 

Sec.  io.  No  person,  firm  or  corporation  shall  injure,  break  or  remove 
any  portion  of  any  man-hole,  lamp-hole,  flush-tank,  catch-basin  or  any  part  of 
the  sewer  system,  or  throw  or  deposit,  or  cause  to  be  thrown  or  deposited  in 
any  sewer  opening  or  receptacle  connecting  with  the  sewer  system,  any  garb- 
age, offal,  dead  animals,  vegetable  parings,  ashes,  cinders,  rags  or  any  other 
matter  or  thing  whatsoever,  except  faeces,  urine,  the  necessary  water-closet 
paper,  liquid  house  or  mill  slops  and  roof  water  by  special  permit. 

WATER    AND    GAS    PIPE. 

Sec.  II.  Any  person,  firm  or  corporation  desiring  to  lay  pipes  for  water, 
gas,  steam,  or  any  purpose,  in  any  street  or  alley  upon  which  sewers  are  laid, 
shall  give  at  least  twenty-four  hours'  notice  to  the  Superintendent  before  open- 
ing the  street,  and  the  manner  of  excavating  for  laying  and  back-filling  over 
such  pipe  shall  be  subject  to  the  approval  of  the  Superintendent.  All  such 
work  shall  be  planned  and  executed  so  that  no  injury  shall  occur  to  any  public 
sewer  or  drain  or  to  any  house  sewer  or  drain  connected  therewith. 

OBSTRUCTIONS. 

Sec.  12.  The  Superintendent  shall  have  the  power  to  stop  and  prevent 
from  discharging  into  the  sewer  system  any  private  sewer  or  drain  through 
which  substances  are  discharged  which  are  liable  to  injure  the  sewers  or 
obstruct  the  flow  of  the  sewage. 

Sec  13.  Before  any  old  private  drain  or  sewer  shall  be  connected  with 
the  sewer  system,  the  owner  of  the  private  drain  or  sewer  shall  prove  to  the 
satisfaction  of  the  Superintendent  that  it  is  clean  and  conforms  in  every  respect 
with  these  rules  and  regulations. 

TRENCHING. 

Sec  14.  The  house  sewer  trench  shall  be  dug  so  as  to  meet  the  public 
sewer  at  the  position  of  the  "Y"  branch,  as  located  by  the  Superintendent. 
The  material  thrown  from  the  trench  shall  be  placed  so  as  not  to  obstruct 
and  so  as  to  cause  the  least  inconvenience  to  the  public.  Proper  barriers  and 
lights  must  be  maintained  on  the  banks  of  the  trench  to  guard  the  public 
against  accidents  during  the  progress  of  the  work.  In  back-filling  the  earth 
shall  be  carefully  rammed  or  flooded  so  as  to  keep  the  pipe  in  proper  position 
and  avoid  settling,  and  no  stone  shall  be  used  in  filling  until  there  has  been  a 
depth  of  two  feet  of  fine  earth  or  gravel  placed  over  the  pipe. 

MATERIAL    FOR    SEWERS    AND    DRAINS. 

Sec  15.  The  house  sewer  from  a  point  three  feet  outside  of  the  house  to 
the  street  sewer,  shall  be  of  first  quality,  salt-glazed,  vitrified  earthenware  pipe, 


CHAP.    XI.  HOUSK    DKAIXAGK    AND    PLUMBING.  245 

unless  laid  less  than  three  feet  deep,  when  it  shall  be  of  heavy  cast  or  wrought 

iron.     Its  interior  diameter  shall  be inches.     Outside  the  curb  line 

it  shall  be inches.     Subsoil  drains  shall  be  of  earthenware  pipes. 

PIPE    LAYING 

Sec.  i6.  The  cover  of  the  "Y"  branch  on  the  sewer  shall  be  carefully 
removed,  so  as  not  to  injure  the  socket.  The  first  length  of  pipe  attached  to 
the  "Y"  branch  shall  be  curved  and  set  so  as  to  give  a  good  fall  into  the  sewer. 

The  pipe  shall  be  laid  on  an  even  grade  of  not  less  than  one-fourth  of  an 
inch  to  the  foot,  unless  by  special  permission  of  the  Superintendent,  in  which 
case  provision  must  be  made  for  regular  and  efficient  flushing. 

Curved  pipe  shall  be  used  for  every  deflection  from  a  straight  line  of  more 
than  six  inches  in  two  feet. 

The  joints  of  the  earthenware  pipe  shall  be  made  with  the  proper  oakum 
or  jute  gasket,  and  pure  cement  of  first  quality;  the  joints  of  the  iron  pipe  shall 
be  of  oakum  and  lead  if  cast-iron  is  used,  or  screwed  joints  with  white  lead  if 
wrought  iron  is  used. 

The  ends  of  all  private  sewers  not  immediately  connected  with  the  plumb- 
ing fixtures  shall  be  securely  closed  by  water-tight  imperishable  material.  If 
lead  pipe,  the  end  must  be  soldered;  if  wrought  iron  pipe,  a  plug  must  be 
screwed  in  the  end;  if  cast-iron  pipe,  a  cast-iron  plug  must  be  calked  in  with 
the  lead. 

Cellars  shall  be  drained,  when  possible,  by  means  of  suitable,  properly 
laid  earthenware  tile  pipes.  They  shall  not  communicate  directly  with  any 
drain  carrying  foul  sewage,  or  with  a  sewer  or  cess-pool.  Where  possible  they 
shall  connect  with  the  sub-soil  drains  in  the  street. 


PLUMBING  RULES. 


Sec.  17.  All  materials  used  must  be  of  good  quality  and  free  from  defects; 
the  work  must  be  executed  in  a  thorough  and  workmanlike  manner. 

From  a  point  three  feet  outside  the  foundation  wall  of  a  building  no 
material  may  be  used  within  the  building  and  connecting  with  the  sewer,  for 
soil,  waste,  or  vent  pipes,  other  than  wrought  or  cast-iron  pipes,  with  securely 
leaded  joints,  or  lead  pipes  with  soldered  or  wiped  joints.  Cement  or  putty 
joints,  tin  or  sheet  iron  pipes,  whether  galvanized  or  not,  shall  not  be  used 

No  soil  or  waste  pipe  shall  have  a  fall  of  less  than  one  inch  in  ten  feet. 


246  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 


Sec.  i8.  All  cast-iron  pipes  must  be  sound,  free  from  holes  or  cracks,  and 
of  the  grade  known  in  commerce  as  extra  heavy,  coated  with  tar  or  asphaltum. 
The  following  weights  per  lineal  foot  will  be  accepted  as  standards: 

2  inches  5j^   pounds  per  lineal  foot. 

3  inches  gj^   pounds  per  lineal  foot. 

4  inches  13     pounds  per  lineal  foot. 

5  inches   17     pounds  per  lineal  foot. 

6  inches  20     pounds  per  lineal  foot. 

All  wrought  iron  pipe  must  be  of  standard  weight. 

All  fittings  used  in  connection  with  such  pipe  shall  correspond  with  it  in 
weight  and  quality.  Where  lead  pipe  is  used  to  connect  fixtures  with  vertical 
soil  or  waste-pipes,  or  to  connect  traps  with  vertical  vent  pipes,  it  must  not  be 
lighter  than  "light  pipe." 

The  arrangement  of  soil  and  waste-pipes  must  be  as  direct  as  possible. 
The  drain,  soil  and  waste-pipes  and  traps  should,  if  practicable,  be  exposed  to 
view  at  all  times,  for  ready  inspection  and  for  convenience  of  repairing.  When 
necessarily  placed  within  partitions  or  in  recesses  of  walls,  soil  and  waste  pipes 
should  be  covered  with  wood-work  so  fastened  with  screws  as  to  be  readily 
removed. 

MAIN,    SOIL    AND    WASTE    PIPES. 

Sec  ig.  A  main  waste-pipe  into  which  wash-basins,  bath-tubs  or  kitchen 
sinks  discharge  must  be  at  least  two  inches  in  diameter,  with  one  and  one-half 
inch  branches. 

The  main  pipe  from  ihe  sewer  connection  to  the  house  tap  must  be  at  least 
four  (4)  inches  in  interior  diameter  at  every  point.  No  trap  or  any  manner  of 
obstruction  to  the  free  flow  of  air  through  the  whole  course  of  the  main  house- 
sewer  or  soil  pipe  will  be  allowed. 

This  may  be  secured  by  an  untrapped  main  house  sewer  and  soil  pipe,  or 
if  a  trap  is  placed  in  the  main  soil-pipe,  by  a  ventilating  pipe  leading  to  the 
roof  from  the  lower  side  of  the  trap  and  a  fresh  air  inlet  connecting  with  the 
foot  of  the  main  soil-pipe  just  above  the  trap. 

Every  vertical,  soil  and  waste-pipe  must  be  extended  at  least  two  feet 
above  the  highest  part  of  the  roof  or  coping.  It  must  be  of  undiminished  size, 
without  return  bend,  with  open  or  basket  end.  It  must  not  open  near  a  win- 
dow nor  an  air  shaft  which  ventilates  living  rooms. 

Soil,  waste  and  vent-pipes  in  an  extension  must  be  extended  above  the 
roof  of  the  main  building,  when  otherwise  they  would  open  within  twenty  feet 
of  the  windows  of  main  house  or  the  adjoining  house. 


CHAP.    XL  HOUSE    DKAINAGK    AND    PLUMBING.  1^41 


JOINTS. 

Sec.  20.  All  joints  in  iron  drain  pipes,  soil-pipes  and  waste-pipes,  except 
where  screw  joints  are  used,  must  be  so  filled  with  oakum  and  lead  and  hand- 
caulked  as  to  make  them  gas  tight. 

All  connections  of  lead  pipes  with  iron  pipes  must  be  made  with  a  brass  or 
lead  sleeve  or  ferrule  of  the  same  size  as  the  lead  pipe,  put  in  the  hub  of  the 
branch  of  the  iron  pipe  and  caulked  with  lead.  The  lead  pipe  must  be  attached 
to  the  ferrule  by  a  wiped  or  over-cast  joint. 

All  connections  of  lead,  waste  and  vent  pipes  shall  be  made  by  means  of 
wiped  joints. 

INSPECTION. 

Sec.  21.  Before  the  fixtures  are  placed  in  connection  with  the  plumbing 
of  any  house  or  building,  and  before  the  soil-pipe  is  connected  with  the  sewer, 
the  outlet  of  the  soil-pipe  and  all  openings  into  it  below  the  top,  shall  be  her- 
metically sealed;  the  pipe  shall  then  be  filled  with  water  to  its  top,  and  every 
joint  be  carefully  examined  for  leaks.  Work  already  in  place  will  be  examined 
by  the  peppermint  or  other  test.  Defective  pipes  discovered  must  be  removed 
and  replaced  by  sound  ones,  and  all  defective  joints  made  tight,  and  every  part 
of  the  work  be  made  to  conform  to  these  rules  and  regulations,  and  subject  to 
the  approval  of  the  Inspector. 

In  cases  where  plumbing  work  has  been  completed  in  a  building  before 
these  rules  and  regulations  came  in  force,  if  the  plumbing  has  been  done  in 
accordance  with  these  rules  and  regulations,  permits  will  be  granted  for  making 
connections  with  the  sewer  as  in  new  work,  but  in  case  the  plumbing  is  not  in 
accordance  with  these  rules  and  regulations,  such  alterations  shall  be  made  as 
the  Superintendent  shall  direct,  to  make  the  plumbing  safe  to  the  persons 
residing  in  the  house,  and  such  as  to  be  no  source  of  injury  or  stoppage  to  the 
sewer.  In  all  cases  the  soil  pipe  shall  pass  through  and  above  the  roof.  Traps 
are  to  be  ventilated,  fixtures  and  pipes  clean,  and  waste  and  soil-pipes  to  have 
sufficient  fall. 


Sec.  22.  Every  water-closet,  urinal,  sink,  wash-tray,  bath-tub,  and  every 
tub  or  set  of  tubs  must  be  separately  and  effectually  trapped.  Traps  must  be 
placed  as  near  the  fixtures  as  practicable.  In  no  case  shall  water  from  bath 
tub  or  other  fixture  be  connected  with  the  water-closet  trap. 

Sinks  in  all  packing-houses,  butcher  shops,  lard-rendering  establishments, 
hotels,  restaurants,  boarding-houses  and  laundries  shall  be  provided  with  a 
suitable  grease  trap.  Wash-rooms  for  carriages  must  be  provided  with  proper 
means  for  intercepting  mud. 


248  TH1<:    SEPARATE    SYSTEM    OF    SEWERAGE. 


VENT    PIPES. 

Sec.  23.  Traps  must  be  protected  from  syphonage,  or  the  waste  pipe 
leading  from  them  ventilated  by  a  special  air  pipe,  taken  out  of  the  crown  of 
trap,  in  no  case  less  than  two  inches  in  diameter  for  water-closet  traps,  and  one 
inch  and  a  quarter  for  other  traps,  except  when  more  than  fifteen  feet  in  length, 
when  it  shall  not  be  less  than  one  and  a  half  inches  in  diameter.  The  vertical 
vent-pipes  for  traps  of  water-closets  in  buildings  more  than  four  stories  in 
height,  must  be  at  least  three  inches  in  diameter,  with  two-inch  branches  to 
each  trap,  and  for  traps  of  other  fixtures  not  less  than  two  inches  in  diameter, 
unless  the  trap  is  smaller,  in  which  case  the  diameter  of  branch  vent-pipe  must 
be  at  least  equal  to  the  diameter  of  the  trap.  In  all  cases  vent-pipes  must  be 
of  cast  or  wrought  iron  and  connected  to  traps  with  brass  or  lead  ferrule. 

Vent-pipes  must  extend  two  feet  above  the  highest  part  of  the  roof  or 
coping.  The  extension  to  be  not  less  than  three  inches  in  diameter  to  avoid 
obstruction  from  frost,  or  they  may  be  branched  into  a  soil-pipe  above  the 
inlet  from  the  highest  fixture.  They  may  be  combined  by  branching  together 
those  which  serve  several  traps.  These  air  pipes  must  always  have  a  continu- 
ous slope  to  avoid  collecting  water  by  condensation. 

No  trap  vent-pipe  shall  be  used  as  a  waste  or  soil-pipe. 

No  brick,  sheet  metal,  earthenware  or  chimney  flue  shall  be  used  as  a 
sewer  ventilator,  nor  to  ventilate  any  trap,  drain,  soil  or  waste-pipe. 

SAFES — RAIN    WATER. 

Sec.  24.  Every  lead  safe  under  a  wash-tray,  urinal,  refrigerator  or  water 
closet  must  be  drained  by  a  special  pipe  not  directly  connected  with  any  waste 
pipe,  soil-pipe  or  sewer.  The  drip  pipe  from  refrigerators  shall  not  be  con- 
nected directly  with  the  soil  or  waste-pipe  or  with  the  sewer. 

Rain  water  conductors  shall  not  be  connected  with  the  sewers  without  a 
special  permit. 

OVERFLOWS  FROM  FIXTURES. 

Sec.  25.  Overflows  from  fixtures  must,  in  each  case,  be  connected  on  the 
inlet  side  of  the  trap. 

WATER-CLOSETS.  * 

Sec.  26.  Water-closets  must  be  of  an  approved  pattern  (pan  closets  being 
absolutely  prohibited),  and  should  be  supplied  from  a  special  tank  placed  over 
them,  in  which  case  the  waste  or  overflow  from  the  tank  must  discharge  into 
the  open  air  of  the  basin  of  the  closet,  and  not  into  the  soil-pipe  directly. 
Direct  service  of  a  water-closet  is  prohibited. 

All  interior  water-closet  compartments  should  be  ventilated  into  air  shafts 
where  possible 


CHAP.    XI.  HOUSl':    DKAIXAGE    AND    PI.UMHIXG.  249 


STRAINERS. 

Sec.  27.  Exit-pipes  to  all  fixtures  except  water-closets  shall  be  furnished 
with  suitable  permanently  attached  strainers. 

Sec.  28.  No  person  shall  place,  or  suffer  to  be  placed,  any  bulky  sub- 
stance in  any  sewer  opening,  or  in  the  house  connections,  or  private  drains 
connecting  with  any  public,  main  or  lateral  sewer,  or  any  substance  having  a 
tendency  to  obstruct  the  free  flowage  of  said  sewers  or  to  damage  them  in  any 
way. 


Sec.  29.  Any  person  violating  any  of  the  provisions  of  these  rules  and 
regulations  shall  be  deemed  guilty  of  a  misdemeanor,  and  upon  conviction 
thereof  be  fined  in  any  sum  not  exceeding  fifty  dollars  nor  less  than  ten  dollars, 

or  imprisonment  in  the for  a  period  not  exceeding   twenty 

days  or  by  both  such  fine  and  imprisonment,  at  the  discretion  of  the  court. 


PLUMBER'S  LICENSE. 

City  of Sewer  Dep.\rtment. 

No I    .. 

hereby  licensed  to  do 

plumbing  and  lay  house  sewers  and  drains  in  connection  with  the  public  sewers 

in  this  city  in  accordance  with  the  provisions  of  an   "Ordinance  No 

fixing  and  regulating   the  use  of  sewers  by  private  individuals  in  the  city  of 


Sewer . 


PLUMBERS  BOND. 


Know  all  Men  by  these  Presents,   that  we 

of  the  City  of as  principal,  and 

and .as  sureties,  are  held  and  firmly  bound  unto  the 

City  of in  the  penal  sum  of Dollars  to  be  paid 

to  the  said,  the  City  of . . .    or  to  its  certain  attorney,  successors  or 

assigns. 


250  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 


For  7vhich  Pavnu-nt  well  and  truly  to  be  made,  we  bind  ourselves  and  our 
heirs,  executors  and  administrators,  jointly  and  severally,  firmly  by  these 
presents. 

Scaled  this day  of in  the  year  of  our 

Lord  one  thousand 

Wh,-r,'as,  The  said  party  of  the  first  part  has  made  application  to  be 
licensed  to  engage  in  the  business  of  plumbing  in  connection  with  the  public 
sewers  of  said   city,    which   license   has  been  granted,    conditioned    upon    the 

execution  of  this  bond,  as  provided  by  Ordinance  No of  the  Common 

Council  of  said  city,  passed 

Now,  thei-efore  the  Condition  of  this  Obligation  is  such.  That  if  the  said 
party  of  the  first  part  shall  well  and  faithfully,  and  in  a  workmanlike  manner 
perform  the  work  of  connecting  such  sewers,  and  shall  save  and  indemnify  the 
party  of  the  second  part  of  and  from  all  costs,  damages  and  expenses  arising 
from  making  such  connections,  or  the  negligence  or  carelessness  of  the  party  of 
the  first  part,  his  agents,  servants  or  employees  in  making  the  same,  then  this 
obligation  to  be  void,  otherwise  to  remain  in  full  force  and  virtue. 

Sealed  and  delivered  in  the  presence  of 


APPLICATION  FOR  PLUMBING. 
To  the  Department  of  Sercers , 


No I.... 

The  undersigned  applies  for  permission  to  connect  premises  No 

Street,  with  the  public  sewer  in 

Street,  and  to  do  the  necessary  plumbing,    and   I   hereby  desire  a  permit  to  be 

issued  to   ,  a  regularly  authorized  and  licensed 

plumber. 

I  hereby  stipulate  and  agree  that  the  work  on  said  sewer  shall  be  executed 
in  strict  conformity  with  the  provisions  of   "An  ordinance  fixing  and  regulating 

the  use  of  sewers  by  private  individuals  in  the ....," 

and  the  plans  and  specifications  approved  by  the  Superintendent  of  Sewers  in 

And  the  undersigned  further  agrees  that  all  claims 

against  the  City  of for  damages  occasioned  in  any  manner 

by  the  putting  in  of  said  sewer  shall  be  waived,  and  held  null  and  void. 

Owner. 


CHAP.    XI.  HOUSI-:    DKAINAGK    AND    PLUMBINCr,  2.1 1 

PERMIT  TO  CONSTRUCT  SEWER. 

No I.... 

Authority  is  hereby  given  to 

to  execute  the  work  for 

upon  the  terms  and  conditions  specified  in  above  application. 


No  dwelling"  of  any  pretentions  is  now  considered  com- 
plete or  even  looked  upon  with  favor  by  a  prospective  tenant, 
unless  it  is  fitted  with  "modern  conveniences."  These 
appliances  are  entirely  proper  and  safe  if  the  work  is 
entrusted  to  proper  hands.  It  is  hard  to  conceive  of  a  class 
of  work,  however,  in  which  wrong-  methods  or  poor  work  are 
more  detrimental,  or  the  resulting-  influences  more  insidious. 

House  Drainage. — House  drainag-e  in  its  broader  sense 
means  both  the  removal  of  the  liquid  waste  and  whatever  it 
carries  with  it,  and  also  the  removal  of  the  subsoil  water  and 
storm  water.  Indeed,  what  is  often  spoken  of  as  house 
drainag-e  is  strictly  house  sewerag-e.  House  drainag"e  is  the 
removal  of  ground  water. 

The  Subsoil. — The  principal  distinction  between  a 
sewer  and  a  drain  is  that  the  former,  being-  for  the  convey- 
ance of  foul  liquid,  should  be  absolutely  tig-ht,  so  that  none  of 
the  contents  may  be  lost  by  the  way,  and  no  vapors  escape. 
A  drain,  on  the  contrary  (as  for  instance  a  subsoil  drain), 
must  be  laid  with  open  joints,  so  that,  the  pressure  being- 
from  without,  it  will  receive  the  g-round  water  all  along-  its 
course,  and  remove  it.  The  functions  of  the  two  are  dis- 
tinct. When  both  kinds  of  drainag-e  are  necessary,  it  is  best 
to  keep  each  system  distinct.  When  a  g-eneral  system  of 
sewerag"e  is  already  constructed  without  reg-ard  to  subsoil 
drainag-e,  the  householder  frequently  has  no  option  but  to 
connect  the  drainag-e  system  with  the  sewer  proper.  A 
very  g-ood  method  in  such  a  case  is  to  make  the  connection 


252  THE   SEPARATE   SYSTEM    OF    SEWERAGE. 

throug"h  the  medium  of  a  deep  seal  trap  where  the  street 
sewer  enters  the  house.  This  connection  should  be  through 
an  iron  pipe,  properly  caulked  into  the  trap,  and  provided 
with  a  brass-seated  check  valve  which  will  prevent  the  sew- 
ag"e  from  fillings  the  subsoil  drains,  in  case  the  street  sewer 
becomes  obstructed.  The  subsoil  drains  should  be  of  small 
ag"ricultural  tile  laid  well  below  the  cellar  bottom,  and  the 
joints  properly  protected.  The  sides  and  bottom  of  the  cel- 
lar or  basement  should  be  thoroug^hly  damp  proof.  We  are 
aware  that  this  point  is  g^enerally  overlooked.  We  do  not 
stop  to  consider  that  the  earth  below  and  about  building-s  is 
a  great  collector  and  retainer  of  filth,  and  that  it  is  suffi- 
ciently porous  to  admit  of  the  passage  of  air  currents  in  con- 
siderable volume,  especially  under  the  influence  of  furnace 
draughts  or  other  like  causes.  The  action  is  not  unlike 
what  would  occur  if  we  suppose  the  house  set  on  a  sponge 
50x100  feet,  for  instance,  to  which  we  constantly  apply  a 
stream  of  foul  liquid,  and  then  induce  upward  currents 
through  the  house  by  the  action  of  heat.  The  cellar  walls 
and  floor  can  be  very  easily  and  cheaply  made  damp-proof 
and  air-tight  by  a  coating  of  some  preparation  of  asphalt. 

House  Sewers. — One  of  the  most  common  blunders  in 
house  drainage  is  in  making  the  house  sewer  too  large.  It  is 
very  rare  that  any  house  will  require  a  house  drain  (i.  e.  the 
pipe  which  carries  the  sewage  from  the  house  to  the  public 
sewers)  more  than  four  or  five  inches  in  diameter,  and  yet  it 
is  not  uncommon  to  find  a  private  house  provided  with  a 
drain  large  enough  to  carry  the  sewage  of  a  town  of  five 
thousand  inhabitants.  This  use  of  unnecessarily  large  pipe 
arises  from  two  causes.  The  ignorance  of  the  owner,  who 
not  knowing  what  is  required,  determines  "to  have  it  big 
enough,  any  way,"  and  the  cupidity  of  the  plumber,  who 
favors  any  plan  which  swells  the  amount  of  his  bill.  Any 
unnecessary  addition  to  the  size  of  a  house  drain  not  onl}- 


CHAP.    XI.  HOU.SI':    DRAINAGE    AND    PLUMBING.  253 

causes  needless  expense,  but  renders  it  more  difficult  to 
flush  the  drain  and  keep  it  clean.  This  point  has  been  fully 
discussed  in  Chapter  VI. 

The  practice  of  placing^  the  house  sewer  beneath  the 
cellar  floor  is  very  objectionable  for  two  reasons:  It  is  out  of 
sio^ht  and  cannot  easily  be  inspected,  and  it  is  usually  laid  on 
too  flat  a  gfrade,  especially  when  it  runs  beneath  the  floor  for 
a  considerable  distance.  Where  possible  the  pipe  should 
be  placed  along-  the  cellar  wall,  or  hung-  from  the  floor  beams, 
so  that  it  can  be  readily  inspected,  and  can  be  given  a  proper 
grade  to  secure  a  sufficiently  rapid  flow  of  the  sewag-e.  T 
branches  with  tight  covers,  placed  along-  the  pipe  will  afford 
the  means  of  inspecting  the  interior  of  the  drain  and  remov- 
ing- obstructions. 

The  house  drain  within  the  house  should  never  be  of 
earthenware.  It  should  be  of  iron,  and  heavy  enough  to 
admit  of  having  the  lead  joints  caulked  so  as  to  be  water  and 
gas  tight. 

If  roof  water  is  admitted  directly  to  the  sewers,  the 
rain-water  leader  should  connect  with  the  main  soil  pipe 
directly  above  the  main  trap.  No  waste  or  soil  pipe  should 
be  connected  with  the  rain-water  leader.  In  a  great  many 
cases  it  will  be  advisable  not  to  discharge  the  roof  water  into 
the  sewers,  particularly  in  the  case  of  isolated  dwellings 
where  a  portion  of  it  is  retained  by  cisterns,  and  where 
lawns  are  of  considerable  extent.  In  the  case  of  more  com- 
pactly built  city  buildings  it  will  often  be  best  to  allow  the 
roof  water  to  be  discharged  into  the  street  gutters,  espe- 
cially where  these  are  properly  arranged,  and  the  descent  is 
sufficient. 

The  following  table  of  the  behavior  of  house  drains  when 
running  three-fourths  full  was  calculated  by  Robert  Moore, 
C.  E.,  of  St.  Louis,  Mo.:— 


254 


THE    SEPAKATE    SYSTEM    OF    SEWERAGE. 


TABLE  XXVI. 

TABLE    OF    DIAMETERS    OF    HOUSE    DRAINS. 

With  various  grades,   and  for  lots  of  different  sizes,   capable  of  discharging  two 

inches  of  rain  per  hour,   when  running  three-fourths  full. 

Calculated  by  Robert  Moore,  C.  E.,  St.  Louis,  Mo. 


FALL    PER    lOO. 


SIZE  OF  LOT  IN   FEET. 


20x150 3>^ 

25x150 3H 

30x150 4 

35x150 ^H 

40x150 4>^ 

45x150 1  4U 

50x150 5 

60x150 5^ 

70x150 5^ 


80x150 

90x150 

100x150 


6 

6/2 


I.O     1.5     2.0     2.5     3.0     4.0 


DIAMETERS    IN    INCHES. 


■3/8 

4 

4X 
4'A 
5% 

6 


3 

3% 
3A 
3% 
3'A 
4/8 
4X 
A'A 
4% 
5X 

5A 


2% 

3% 

3H 

3% 

3% 

4 

4/8 

4^8 

4I4: 

5 

5^ 

5% 


3 

3% 

3/2 

3H 

3V& 

4 

4X 

^A 

A% 

5 

5% 


1% 

2% 

3 

3% 

3/2 

3M 

3% 

4 

4^ 

^Vz 

4^/4 


5.0 


2>^ 

2^ 

3 

3% 
3X 
3^ 
3% 
3H 

4/4 
4U 


By  an  inspection  of  the  Table,  we  see  that  a  four-inch 
main  house  sewer  is  ample  for  any  ordinar}^  condition  of 
service,  even  if  roof  water  be  admitted,  the  discharg-e  of 
house  sewagfe  proper  being*  only  a  very  small  percentage  of 
the  total  volume.  A  smaller  size  than  four  inches  is  not  to 
be  recommended,  however,  for  the  reason  that  althoug-h  it 
may  be  ample  so  far  as  estimated  carrying"  capacity  is  con- 
cerned, it  is  more  liable  to  obstruction.  Under  some  cir- 
cumstances it  ma}^  be  advisable  to  increase  the  size  of  the 
main  drain  to  five  or  even  six  inches  diameter,  this  limit 
should  not  be  exceeded  however.  If  one  drain  of  this  size  is 
not  ample  it  is  better  to  increase  the  number. 

In  order  to  provide  for  ventilating  the  house  drain  it 
should  be  carried  full  size  up  through  the  roof.     This  venti- 


PLATE  XXVIII. 


INTERIOR    PLUMBING. 


CHAP.  XI.  HOUSK    DKAINAGI-:    AND    PLUMBING.  2.3  1 

lation  of  house  drains  has  been  discussed  in  a  previous  chap- 
ter. 

Grease  Traps. — The  principal  dang-er  of  stoppag^es  in  a 
house  drain,  properly  laid,  arises  from  the  grease  carried 
into  it  from  the  kitchen  sink.  This  can  be  avoided  by  the 
use  of  a  grease  trap,  placed  under  the  sink.  The  objection 
to  the  use  of  a  grease  trap  is  that  they  need  to  be  cleaned 
occasionally,  and  if  not  cleaned  they  get  very  foul. 

Soil  and  Waste  Pipes. — Soil  pipes,  that  is,  pipes  leading 
from  water-closets,  and  waste  pipes,  that  is,  pipes  leading 
from  bath-tubs,  wash  stands,  etc.,  may  be  either  of  iron  or 
lead.  Iron  is  the  better  material  where  it  can  be  used,  but 
lead  is  easier  to  fit  and  adjust  where  the  connection  between 
the  fixture  and  the  main  drain  is  not  direct.  All  iron  pipes 
should  be  either  enameled  or  coated  inside  and  out  with  coal 
pitch  varnish  to  give  them  a  smooth  surface  and  keep  them 
from  rusting.  All  junctions  and  changes  in  the  direction  of 
the  pipe  should  be  made  by  easy  curves. 

A  very  common  fault  is  to  make  the  upward  extension  of 
the  soil  pipe  after  it  passes  the  highest  fixture,  of  galvanized 
sheet  iron,  or  even  of  tin.  This  is  highly  objectionable.  It 
should  be  of  heavy  iron  pipe  throughout,  and  should  extend 
well  above  the  roof.  It  is  a  good  plan  to  increase  it  in  size 
above  the  roof  to  six  inches,  so  as  to  lessen  the  danger  of  its 
being  obstructed  by  the  accumulation  of  frost.  Ventilating 
cowls  are  of  doubtful  utility.  A  plain  wire  basket  to  pre- 
vent the  introduction  of  articles  liable  to  obstruct  the  pipes 
is  better. 

There  is  such  a  variety  of  branches,  curves,  off-sets, 
traps,  etc.,  etc.,  now  in  the  market,  that  there  is  no  excuse 
for  awkward  and  rough  connections  and  interior  projecting 
angles  or  pockets  which  will  retain  the  solid  portion  of  the 
sewage.     The  course  of  all  pipes  should  be  as  direct  as  pos- 


258  THE    SEPARATE   SYSTEM    OF    SEWERAGE. 

sible,  and  the  fixtures  should  be  grouped  so  as  to  be  reached 
as  nearly  as  possible  by  uprig-ht  soil  pipes  and  short  horizon- 
tal soil  or  waste  pipes.  Horizontal  pipes  cannot  be  carried 
any  g^reat  distance  along-  floors  or  ceiling-s  or  between  joists, 
and  preserve  a  proper  inclination,  for  reasons  which  are 
obvious.  It  is  customary  to  make  waste  pipes,  particularly 
short  ones,  of  lead,  for  the  reason  that  it  is  much  more  easily 
manipulated  than  iron.  The  proper  method  of  connecting- 
the  lead  wastes  to  iron  is  by  means  of  a  thimble  soldered  to 
the  lead  pipe  and  caulked  into  a  hub  on  the  iron  pipe. 

Traps  and  Ventilation. — Every  fixture  should  be  pro- 
vided with  a  trap,  and  since  the  object  of  the  trap  is  to  iso- 
late the  fouled  interior  surface  of  the  waste  pipe  from  the  air 
of  the  room  it  is  evident  that  the  trap  should  be  as  close  to 
the  fixture  as  possible.  Notwithstanding-  many  efforts  to 
introduce  a  trap  whose  seal  cannot  be  broken  by  syphonag-e, 
and  which  will  be  self-cleansing,  the  plain-running-  trap  of 
uniform  bore  is  still  in  g-eneral  use.  This  trap  is  liable  to 
have  its  seal  broken  by  syphonag'e,  and  to  prevent  this  it  is 
necessary  to  resort  to  a  back  air  pipe,  which  is  connected 
with  the  crown  of  the  trap  on  the  downward  side,  and  passes 
to  the  roof  independently  of  the  ventilating-  pipe  proper,  or  is 
connected  with  it  above  the  hig-hest  fixture.  This  back  air 
pipe  should  be  of  ample  capacity  to  preserve  the  equilibrium 
of  air  pressure. 

The  system  of  back  air  vents  is  open  to  the  following^ 
objections:  It  considerably  complicates  the  system  of  pip- 
ing-, especially  w'here  fixtures  are  not  closely  g-rouped. 
There  is  a  possibility  of  the  pipes  being-  fouled  at  their  junc- 
tion with  the  crown  of  the  trap.  It  adds  considerably  to  the 
expense. 

Back  air  vents  tend  to  increase  the  interior  circulation  of 
air  considerably.  This  is  beneficial,  so  far  as  purity  of  the 
interior  of  the  pipes  is  concerned,   but  it  also  increases  the 


CHAP    XI.  HOUSH    DKAINAGK    AND    PLUMBING.  259 

evaporation  from  traps.  This  will  do  no  harm  if  fixtures 
are  in  constant  use.  On  the  other  hand,  if  special  anti- 
syphoning-  traps  are  used,  and  back  vents  are  dispensed 
with,  there  will  be  little  circulation  of  purifying  outer  air 
throug-h  the  waste  pipes. 

General  Features. — Corners  and  recesses  within  the 
pipes  and  plumbing-  fixtures  should  be  avoided.  All  interior 
surfaces  should  be  thoroug-hly  flushed  at  every  rush  of  water 
throug-h  the  pipes,  otherwise  the  animal  matter  left  sticking- 
to  the  surface  will  decompose  and  send  off  foul  g-ases.  On 
this  account  the  use  of  "pan  closets,"  and  many  patterns  of 
traps,  should  be  discontinued.  The  plumbing-  fixtures  in  a 
house  should  be  as  few  as  possible.  Not  only  is  every  addi- 
tional fixture  and  pipe  joint  a  possible  source  of  dang-er,  but 
the  principal  danger  from  sewer  g-as  arises  from  rarely  used 
fixtures,  from  which  the  water  in  the  traps  has  evaporated. 

The  fixtures  on  the  different  floors  should  be  arranged 
so  as  to  have  them  as  nearly  in  a  vertical  line  as  possible,  in 
order  to  avoid  running  waste  and  soil  pipes  horizontally  or 
with  insufficient  fall. 

The  less  wood-work  around  fixtures  the  better.  Not 
only  does  the  wood  itself  become  foul,  but  the  space  within 
the  casing  is  dark,  damp  and  dirty — a  favorable  locality  for 
mould  and  rot,  and  a  breeding  place  for  vermin. 

Unwholesome  smells,  which  are  attributed  to  some 
faulty  construction  or  arrangement  in  the  drainage  pipes, 
often  have  their  origin  in  these  inclosed  spaces. 

It  is  not  uncommon  in  summer,  when  the  air  is  loaded 
with  moisture,  to  see  water  accumulate  in  bead-like  drops  on 
the  surface  of  plumbing  fixtures  or  pipes  which  are  kept 
cool  by  a  current  of  water  from  a  tap,  and  bourse  downward 
almost  in  streams.  If  the  fixtures  are  not  inclosed  they  can 
be  readily  wiped  dry.     If  inclosed  they  receive  no  attention, 


260  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

and  the  accumulation  of  dirt  and  moisture  becomes  very 
offensive. 

The  better  kinds  of  water  closets  are  made  so  as  to 
require  no  wood  surrounding-  them,  except  a  cover.  A  very 
g-ood  way  to  fit  up  wash  stands  is  to  support  the  slab  upon 
brackets  fastened  to  the  wall,  leaving"  the  under  side  entirely 
open,  and  the  pipes,  traps,  etc.,  entirely  exposed,  or  par- 
tially hid  by  a  narrow  slab  placed  edg-ewise  under  the  shelf 
proper,  and  extending"  downward  about  six  inches. 

So  far  as  possible  it  is  preferable  to  have  soil,  waste  and 
ventilating"  pipes  exposed,  to  having"  them  inclosed  within 
partitions  where  they  are  inaccessible  either  for  inspection 
or  repair. 

This  method  of  arrang"ement  is  not  without  its  influence 
on  the  plumber.  He  is  not  less  inclined  to  pour  lead  joints 
properly,  or  to  thoroughly  caulk  them  all  around,  or  to  make 
neat  and  perfect  wiped  joints,  than  when  he  knows  that 
the  carpenter  or  plasterer  will  cover  his  work  within  a  few 
hours.  The  average  house  owner  will  look  upon  this 
arrangement  as  decidedly  lacking"  in  finish  and  not  in  har- 
mony with  interior  decorations.  Neither  is  a  stove  pipe,  a 
furnace  reg"ister,  a  steam  radiator,  or  a  g"as  fixture.  This  is 
larg"ely  a  matter  of  education,  and  possibly  we  have  been 
wrong"ly  taug"ht.  It  is  not  customary,  however,  to  place 
these  fixtures  in  rooms  where  any  exceptions  can  be  taken 
to  this  method  of  arrang"ement. 

The  common  practice  of  placing  water  closets  and  other 
plumbing"  fixtures  in  dark,  ill-ventilated  places,  such  as 
inside  rooms,  dark  closets,  under  stairways,  etc.,  is  wrongs  in 
every  way.  All  plumbing"  fixtures  and  pipes  should  as  far  as 
possible,  be  kept  open  to  the  air  and  lig"ht.  The  places 
which  are  naturally  the  most  foul  stand  most  in  need  of  sun- 
lig"ht  and  pure  air. 

Where  it  is  possible  to.  avoid  it,  no  plumbing  fixtures 
should   be   placed   in   a   bedroom.       During"  the  night   some 


CHAP.  XI.  Housio  dkainagp:  and  plumbing.  261 

decomposition  will  be  gfoing-  on  abov^e  the  trap  in  any  fixture, 
and  some  foul  g"as  will  be  g^iven  off.  This,  with  the  chance 
of  sewer  g^as  coming-  in  through  some  defective  joint,  pipe  or 
trap  makes  the  risk  too  g^reat  to  be  taken  if  it  can  be  avoided. 
They  should  be  confined  to  the  bath  room,  where  special 
means  of  ventilation  can  be  employed,  and  to  the  kitchen 
laundry  and  similar  rooms. 

A  multiplicity  of  fixtures  should  be  discourag^ed.  A 
fixture  rarely  used  is  a  greater  source  of  dang-er  than  one 
used  frequently.. 

Particular  care  should  be  used  in  arranging-  the  ventila- 
tion of  a  building,  so  that  the  air  currents  tend  to  pass  out- 
ward from  the  g-roup  of  rooms  containing*  plumbing-  fixtures, 
fresh  air  being-  admitted  to  other  portions  of  the  building-. 
The  facility  with  which  this  can  be  accomplished,  and  also 
the  proper  g-rouping-  of  fixtures  and  simplicity  of  the  system 
of  pipes  will  depend  larg-ely  upon  the  architect. 

The  ornamentation  of  porcelain  ware  and  of  surround- 
ing wood-work  by  raised  or  carved  patterns  is  positively 
detrimental.  A  perfectly  plain,  smooth  impervious  surface 
is  more  conducive  to  cleanliness. 

Everything-  connected  with  house  drainag-e  and  plumb- 
ing- should  be  of  the  best  material  and  most  thoroug-h  work- 
manship. The  best  plumbing  is  not  too  good.  By  best 
plumbing-  is  not  meant  the  most  showy,  or  necessarily  the 
most  expensive.  Water  closets  and  sinks  are  not  the  most 
appropriate  places  for  g-ilt  and  tinsel.  On  the  other  hand,  it 
is  poor  economy  to  risk  health  and  life  on  cheap,  bad  work 
in  the  sanitary  arrangements  in  our  homes. 

When  the  soil,  ventilating-  and  waste  pipes  are  all  in 
position,  and  before  the  fixtures  are  put  in  place,  a  test  of 
the  thoroug-hness  of  the  work  should  be  made.  This  can  be 
done  in  a  variety  of  ways.  The  following-  will  be  a  very  g-ood 
test:  Close  up  the  main  drain  where  the  iron  pipe  termi- 
nates outside   the  house  wall,  also  the  exposed  ends  of  all 


262  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

pipes  where  fixtures  are  to  be  connected,  and  the  fresh  air 
inlet,  if  there  is  any.  The  ends  of  lead  pipes  should  be  left 
somewhat  long-er  than  necessary,  so  that  this  can  be  conven- 
iently done  by  flattening-  them  and  closing-  with  solder. 

When  all  openings  in  the  entire  system  of  soil,  waste 
and  ventilating  pipes  are  tightly  closed  below,  fill  the  entire 
system  with  water  from  above  nearly  to  the  top,  and  mark 
the  heig-ht  at  which  the  water  stands.  If  no  leakage  is 
apparent  and  the  water  stands  at  the  same  level  for  some 
hours,  the  joints  may  be  considered  good.  The  entire  work 
should  be  carefully  inspected  while  under  pressure,  and 
joints  re-caulked  where  necessary. 

It  is  not  proper  to  connect  waste  pipes  from  refrigera- 
tors or  safes,  or  overflow  pipes  from  water  tanks  or  cisterns 
directly  with  the  sewers  or  waste  pipes.  The  discharg-e 
from  these  can  be  often  collected  at  a  common  receptacle, 
however,  which  is  isolated  from  the  sewers  by  special 
means. 


CHAPTER  XII. 

COST  AND  ASSESSMENTS. 

Comparative  Cost  of  the  Separate  and  Combined  Sys- 
tems.— No  grneral  comparison  of  the  economy  of  the  Sepa- 
rate and  Combined  Systems  of  seweragfe  can  be  made.  It 
depends  in  all  cases  on  the  condition  of  each  problem,  and 
the  relative  economy  in  a  particular  case  can  be  determined 
only  by  a  competent  eng"ineer,  after  thoroug-hly  considering- 
the  requirements  to  be  met. 

As  indicated  in  a  previous  chapter,  there  can  be  no  ques- 
tion as  to  which  system  will  secure  the  most  perfect  and 
sanitary  house  drainag^e,  whatever  the  conditions  may  be. 
In  the  Separate  System  proper  we  are  seeking"  this  with  a 
sing-le  aim,  and  may  adopt  anything"  conducive  to  it  and 
reject  anything-  detrimental  to  it.  How  far  we  may  depart 
from  this  line  from  considerations  of  apparent  economy  is  a 
serious  question. 

It  must  not  be  forg-otten  that  we  are  establishing-  a  com- 
plete svstem  of  subterranean  communication  between  the 
dwelling-s  of  all  classes  of  society,  interposing-  but  a  small 
volume  of  water  as  a  barrier  to  the  circulation  of  air  cur- 
rents, and  when  street  water  is  admitted  we  are  introducing- 
another  element  of  dang-er. 

In  many  of  the  smaller  cities  of  the  United  States  (and 
they  are  comparatively  numerous,  as  shown  in  Table  II) 
there  can  be  no  question  as  to  the  superior  advantag-es  of  the 
Separate  System  in  economy,  efficiency,  and  adaptability  to 
all  the  requirements  to  be  met.  In  cities  of  this  class  it  is 
folly  to  construct  a  Combined  System  ill  adapted  to  the  work 
in  hand.  The  question  of  relative  cost,  thoug-h  favoring-  the 
Separate  Sys^tem,  is,  therefore,  not  a  pertinent  one. 


264  THE    SEPARATE   SYSTEM    OF    SEWERAGfc:. 

A  comparison  as  to  cost  can  only  be  properly  drawn  in 
the  case  of  cities  where  considerable  areas  are  paved  and  the 
storm  water  from  them  cannot  be  carried  to  the  nearest 
stream  without  accumulating-  in  the  g^utters  to  a  deg^ree 
interfering-  with  business  or  threatening  damag"e  to  prop- 
erty. 

The  admission  of  storm  water  to  small  streams  travers- 
ing- a  city  is  entirely  proper  and  generally  beneficial.  Any 
filth  broug-ht  from  foul  pavements  is  thoroughly  removed  by 
the  after-flow  of  the  rain  which  bring-s  it,  and  also  the  filth 
accumulated  in  the  bed  of  the  streams  during-  low  stages  of 
water,  which  is  so  potent  a  factor  in  pollution  and  the  accu- 
mulation of  which,  despite  the  string-ent  ordinances  in  force 
in  cities  of  this  class  ag-ainst  the  pollution  of  streams,  it 
seems  well  nig^h  impossible  to  prevent. 

Even  in  the  Combined  System  it  is  usual  to  provide  over- 
flows for  the  escape  of  a  portion  of  the  storm  water  into  the 
natural  drainag-e  channels. 

"No  system  of  sewerage  yet  proposed  in  any  city  contemplates  the  removal 
of  excessiTi-  storm  water  by  means  of  sewers  alone — such  storms,  for  instance, 
as  discharge  for  short  intervals  two  or  three  inches  of  rain  in  an  hour  These 
occur  at  long  intervals  and  are  of  short  duration  and  the  damage  is  usually 
confined  to  limited  areas,  while  the  construction  of  sewers  to  meet  the  contin- 
gency would  be  attended  with  enormous  expense  over  the  whole  city,  both  in 
construction  and  repair,  and  prove  of  doubtful  efficiency  when  suddenly  called 
upon,  and  extremely  objectionable  as  conduits  for  the  ordinary  flow  of  sewage.' 
— Adams. 

In  cities  of  this  class,  then,  we  may  properly  compare 
the  cost  of  the  Combined  System  uniting-  the  house  and  man- 
ufacturing- wastes  with  the  storm  water  for  removal  in  the 
same  conduit  on  one  hand,  with  the  cost  of  the  Separate  Sys- 
tem proper,  supplemented  by  conduits  for  the  separate 
removal  of  surface  water,  where  such  are  necessary,  dis- 
charg-ing-  into  the  nearest  water-course.  Sewers  for  house 
drainag-e  are  required  in  every  street  or  alley.  Conduits  for 
the  removal  of  storm  water  from  streets  are  required,  with 


CHAP.   XII.  COST    AND    ASSESSMENTS.  265 

rare   exceptions,    only  in  alternate  streets,    extending-  from 
the  natural  drainag^e  channels  toward  the  summits. 

It  will  thus  be  seen  that  even  in  very  densely  built  por- 
tions of  a  city,  if  the  sewag"e  proper  can  be  combined  with 
the  storm  water  without  necessitating"  an  extension  of  the 
larg-e  out-fall  sewer,  which  otherwise  would  not  be  required, 
the  sewers  in  alternate  streets  extending-  parallel  with  storm 
water  conduits,  and  in  every  street  intersecting-  them,  may 
receive  house  drainag-e  exclusively,  to  be  linally  discharg-ed 
into  the  common  out-fall. 

In  this  case  if  the  city  be  laid  out  in  reg-ular  squares,  the 
Separate  System  will  reach  three-fourths  of  the  dwelling's 
without  requiring-  a  double  system  in  any  street. 

It  often  happens,  however,  that  j^uch  a  combination  can- 
not be  made  without  requiring-  the  construction  of  a  long-  line 
of  out-fall  sewer  of  larg-e  diameter,  at  a  comparatively  larg-e 
cost,  which,  if  the  storm  water  was  not  combined  with  the 
sewag-e,  mig-ht  be  of  comparativeh'  small  size  and  cost. 

In  desig-ning-  a  system  of  sewerag-e,  then,  the  vital  ques- 
tion is  not  properly  that  of  the  comparative  cost  of  the  Sep- 
arate and  Combined  Systems,  but  a  question  of  the  proper 
means  to  be  adopted  for  doing-  the  work  required  to  be  done. 

Cost  of  the  Separate  System. — The  principal  items  in 
the  cost  of  sewers  are:  the  pipe,  trenching,  laying-  pipe  and 
refilling  the  trench,  man-holes,  flush-tanks,  lamp-holes  and 
eng-ineering-  and  superintendence. 

The  pipe  manufacturers  issue  price  lists,  and  these 
with  the  discount  (depending  upon  the  season,  amount 
required,  etc.)  can  be  obtained  by  applying-  to  the  ag-ents  or 
g-eneral  offices. 

The  only  very  uncertain  item  in  the  list  is  the  second — 
trenching-,  laving  pipe  and  refilling-.  This  will  depend  upon 
the  nature  of  the  soil  in  which  the  sewer  is  laid. 


266  THE   SEPARATE    SYSTEM    OF^    SEWERAGE. 

Quicksand  is  the  most  difi&cult  material  to  manag"e.  It 
will  cost  from  two  to  five  times  as  much  to  put  in  a  sewer  in 
quicksand  as  it  will  in  ordinary  earth. 

Examples  of  Cost  from  Actual  Work. — As  a  g"uide  in 
estimating"  the  cost  of  sewers  of  the  Separate  System  a  few 
instances  of  the  cost  of  actual  work  are  here  g"iven. 

In  Table  XXVII  will  be  found  a  statement  of  bids 
received  on  sewer  construction  in  Schenectady,  N.  Y. 

The  soil  in  which  these  sewers  were  proposed  to  be  laid 
was,  for  the  most  part,  favorable.  It  was  necessary,  how- 
ever, to  sheet  pile  the  trenches  nearly  all  the  way.  Very 
little  hardpan  was  met  in  construction.  About  1,500  feet  of 
the  Front  Street  main  sewer  was  laid  in  quicksand,  the 
water  rising-  to  an  average  depth  in  the  trenches  of  about 
two  and  one-half  feet.  The  cut  under  the  New  York  Cen- 
tral Railroad,  on  Front  Street,  was  peculiarly  difficult,  the 
depth  of  trench  at  this  point  being-  sixteen  and  one-half  feet, 
the  lower  four  feet  of  which  was  quicksand  and  Wciter. 
More  or  less  quicksand  and  water  were  encountered  on  all 
the  streets  leading-  from  the  lower  levels  of  the  town  to  the 
plateau  on  the  east,  and  also  in  White,  Romeyn,  and  Fonda 
Streets,  South  Avenue  and  Nott  Terrace.  On  the  eig-hteen- 
inch  main  in  Fonda  Street  about  two  hundred  feet  of  rock 
work  was  encountered,  averag-ing-  about  two  and  one-half  feet 
deep.  It  was  removed  by  the  contractor  at  a  cost  of  about 
ninety  cents  per  cubic  yard  and  no  extra  allowance  was 
made  therefor. 

The  conditions  found  in  Schenectady  do  not  seem  to  be 
widely  at  variance  with  those  ordinarily  met  with. 

The  contract  was  awarded  to  the  bidder  whose  name 
appears  twelfth  in  the  schedule  of  bids,  at  the  prices  therein 
stated. 

Ninety-seven  per  cent,  of  the  work  was  completed 
within  six  working-  months. 


30  »ft  -*  M  »n 

O  O  O  -  O 


1  O  O  fnao 
«  ■-  o  o 


-joqcf  pne 
sjoif-dmci  isd  aoiJd 


w 

o  o  o  > 

ns.00<o0030>n00 

moo  O  < 

■<  00  >n  o  -  ao  r^  -s-o  i^  -  in 

•joqEi  puE 
■jjUEj-qsng  iad  sauj 


•ioqei  puE 
sjEuajEtn  auipnioai 
'aioq-nEtn  jad  aoud 


owoo'dSoSSoSoSoo 
r»  N  o  o  m  u-i  m  o  o  >n  o  m  d  o  4- 


-9- t^l^  ■«-X 


8<MOOmOCOOOOOOO 
ooor~sOCOocoooc 

0OPl*-3C    -*-ioOO»n  w^vc   o    ^  o 


•adid  qoui-gi  SuiXei 
pue  Suiqsiujnj  joj 
jooj  |E3ni[  jad  aouj 


•adid  qoai-zi  Sui.<e| 
ptie  Suiqsiujnj  Joj 
)oo}  leaai)  jad  aouj 

•adid  qoni-oi  Snivel 
puE  Siiiqsiuinj  joj 
jooj  lEanii  jad  aoijj 


I  vo  r^  o  »n  ^3D  o  »n  o  o  M 


O  vC  30  u-»o  w-i  o  r^  >n  «^.o 


H-  X  30  >nx  fo  o  «  c^»o  r-%  w  r^  o  o 


Orv»-'rxO'^**^  '^^  f^  o 


•adid  qoui-s  Huiaei 
puB  Saiqsiujnj  joj 
jooj  [Eauii  jad  aou^j 


•jaaj  91  japun  puB 

jaaj  ti  jaAO  Suijm 

-SJDEq  puE  nojiBAEOxa 

JOJ  jooj  jad  aoijj 


1  N   N   M  «    —    M    ^ 


oomooor^ooooc 


■jaaj  ti  japun  poB 
laaj  zi  jaAO  Suijig 

-^OEq    pUE  UOIJEAEOXa 

JOJ  JOOJ  jad  aoijj 


ONO«m»nr«0-^0»nO»riON 
•^  I-  mrsinoo  r^r^mM  -^-c^  moo 


•jaaj  zi  japun  puE 
jaaj  01  JBAO  3u!i|iJ 

-JJOBq   pUE  UOlJEABDSa 

JOJ  JOOJ  jad  aoUfj 
•jaaj  01  japnn 
pnB  jaaj  g  jbao  Suing 

-SJOEq  pUB  UOIJBABOXa 

JOJ  JOOJ  jad  aouj 


m\o  O  CTiOnOvO  O  M*nO  mmo  ' 
0\  c\  O  m  ro  o  »rjo  ^  0\  ^  cox  w  ' 


OOOTj-'^NOXWrnOO  »nx  N 

cr\  t^x  m  mio  tn  ■^  m  invo  (n  f^  »-«  'i- 


■jaaj  8  japun  puB 
jaaj  9  jaAO  3u![ig 

-3(DBq  pUE  UOIJEAEOXa 

JOJ  JOOJ  jad  aoiJd 
■jaaj  9  japun  Suing 

->lOBq  pUB  UOIJEAEOXa 

JOJ  JOOJ  jad  aoij(j 


o  -j-t^l^^l'vN  r^x 


;£s 


5-0 


o  -  c 


1/3  X  -AO  ait/iS-x.-J-.x. 


268  THE    SEPARATE   SYSTEM    OF    SEWERAGE. 

The  following-  is  a  detailed  estimate  of  the  work  as 
finally  completed  and  represents  the  total  cost  of  the  work, 
exclusive  of  eng-ineering,  expenses  of  sew^er  commission, 
land  damag-es,  preparation  of  plans,  records,  etc.: 

Excavation $10,823  43 

Pipe  and  laying 12,229  37 

Accessories 5.739  87 

Total,  $28,792  67 

A  total  cost,  for  construction  proper,  of  $.55  per  lineal  foot. 

The  work  afforded  the  contractor  a  reasonable  profit, 
but  it  is  doubtful  if  at  present  prices  it  could  be  duplicated. 
At  the  time  bids  were  submitted  common  laborers  could  be 
hired  at  from  one  dollar  to  one  dollar  and  twenty-five  cents 
per  day. 

Prices  of  material  were  also  depressed.  The  entire 
cost  of  the  system,  including  man-holes,  flush-tanks  and  all 
accessories,  all  expenses  of  engineering,  and  preparation  of 
plans  and  records,  expenses  of  sewer  committee,  and  all 
costs,  of  whatever  nature,  chargeable  to  the  sewers  was  $.72 
per  lineal  foot. 

A  tax  of  $2.50  per  capita  on  the  population  accommo- 
dated by  these  sewers,  or  a  tax  of  one-half  of  one  per  cent, 
on  the  assessed  valuation  of  the  city  would  have  paid  their 
cost. 

In  Table  XXVIII  will  be  found  a  statement  of  bids 
received  for  the  construction  of  a  system  of  sewers  in  West 
Troy,  N.  Y.  The  contract  was  aw^arded  to  the  bidder 
whose  name  appears  first  in  the  Table. 


■siaEX-qsnij 


•3[Ofj-dniET 


•piB[  nox  J3d  adij  nojj 


■jjaoj  JO}  qidsp  ui  -jj 
joj  ijieauiT  jad  gDuj 


'SaiAcds^ 


•piBj  niBJd  aiij[  qouj-E 


■piEi  ad[d  qoui-gi 


•piB]  adid  qoai-Si 

«ft 

in 

00 

00 

m 
•^ 

0 

t^ 

-r 

IT) 

M 

•piE|  adfd  qouj-zi 

<» 

o 

N 
•^ 

■piB[  adij  qoni-oi 

^ 

O 
m 

o 

O 

o 

O 

•piBi  adid  qoai-g 


■piBi  adij  qaui-g 


■jaaj  91  oj  ti  ^niiitjj 
-5jOEg  puE  BauBAEoxg 


■jaaj  t-i  OJ  zi  Bnifiij 
-JtOBg  puE  anijEAEoxg 


■jaaj  zi  OJ  01  Sujuij 

-5]0Eg  pUB  SuiJEABOXg 


•jaaj  01  OJ  8  SunUH 
-jjOBg  puB  SuijEAEOxg 


-3(3Bg  pOE  auiJEAEOXg 


■jaaj  9  japun  SuiniJ- 
-s^oEg  puB  SuijBABOxg 


"So       '-' 


r     ? 


-^       a, 
n!       O 


2     "^ 


>      S      25 


O 


270  THE    SEPARATE   SYSTEM  OF    SEWERAGE. 

The  g-eneral  statistics  of  the  sewers  are  as  follows: 

Total  leng-th  of  sewers  (18  8-10  miles) 96,319  feet 

Total  cost  (exclusive  of  g^eneral  expenses).S95,241.78 

Total  cost  per  foot         "         "         "     99  cents 

Deepest  trench  (rock ) 16  feet 

Number  of  flush-tanks 116 

Larg-est  size  of  pipe 18  inches 

Smallest  size  of  pipe  (with  few  exceptions).   8      " 

Number  of  canal  crossing's 7 

Number  of  outlets 7 

Long-est  continuous  line  of  sewer.  .  .About  9,000  feet 

Number  of  flushing-  inlets  from  canal 6 

Datum  level Low  water  in  the  Hudson  River 

Leng-th  of  drain  tile 18,926  feet 

The  system  is  almost  entirely  the  Separate  System. 
The  only  exception  being-  a  small  territory  tributary  to  the 
Sixth  Street  main  from  which  surface  water  is  admitted. 
As  will  be  seen  by  the  accompanying-  map,  the  villag-e  has  a 
river  front  on  the  Hudson  of  about  two  miles.  This  affords 
an  opportunity  of  employing-  several  outlets,  and  makes  it 
possible  to  carry  the  sewag-e  to  its  out-fall  in  the  river  by 
short,  direct  lines,  except  in  special  cases.  By  dividing  the 
whole  territory  into  several  distinct  systems,  each  with  a 
separate  outlet,  larg-e  mains  were  avoided  and  the  cost  of 
construction  materially  reduced. 

The  villag-e  extends  back  from  the  river  a.bout  half  a 
mile,  and  as  the  g-eneral  direction  of  the  main  was  towards 
the  river,  no  very  long-  lines  were  necessar}-.  The  surface 
of  the  ground  falls  towards  the  river  with  sufficient  slope  for 
sewer  grades,  so  that  fiat  grades  were  rarely  necessary. 
The  Erie  canal  runs  throug-h  the  villag-e  from  north  to  south, 
nearly  parallel  with  the  river,  and  about  800  feet  from  it. 

The  surface  of  the  water  in  the  canal  is  on  the  averag-e 
about  level  with  the  natural  surface  of  the  g-round  near  the 
canal;  in  places  rising  above,  and  in  places  fallings  below  it. 

Besides  the  main  line  of  the  canal  there  are  two  branch 
canals,   leading-   to   the   river,    and   two  larg-e  basins.       The 


CHAP.    XII.  COST    AND    ASSESSMENTS.  271 

canal,  branches  and  basins,  greatly  complicated  the  work  of 
designing-  the  sewers,  and  increased  the  cost  of  construc- 
tion. 

The  material  to  be  excavated  from  the  trenches  con- 
sisted of  gravel,  sometimes  containing  large  boulders,  clay 
and  rock,  varying  in  quality  from  soft  shale,  which  yielded 
readily  to  the  pick,  to  hard  arg-illaceous  rock,  seamed  with 
quartz. 

The  canal  banks  intercepted  the  natural  flow  of  the 
g-round  water  towards  the  river  and  materially  increased  the 
trouble  from  this  source.  Since  the  water  in  the  canal  was 
about  level  with  the  natural  surface  of  the  ground  near  the 
canal,  it  is  readily  seen  that  the  ground  in  the  vicinity  of  the 
canal  would  be  water-soaked,  and  that  wet  cellars  and  diffi- 
cult trenching-  might  be  expected.  In  several  places  in  the 
village  the  rock  came  to  the  surface  in  ridges,  leaving- 
pockets  of  considerable  extent  without  drainage.  In  these 
places  wet  cellars  were  common.  So  little  attention  had 
been  g-iven  to  drainage  that  in  some  places  stagnant  pools  of 
considerable  extent  remained  all  summer. 

The  following  is  a  statement  in  detail  of  the  cost  of  the 
system: — 

Earth  Excavation $    16,008.23 

Rock  Excavation 26,891.79 

Sewer  pipe  laid  in  the  trench 2.5,716.74 

Drain  tile  laid  in  the  trench 2,41-6.34 

Manholes 4,617.00 

Flush-Tanks  and  connections  and  Flush- 
ing Inlets 11,699.60 

Lamp-Holes 795.00 

Iron  pipe — laid 4,209.26 

Outlets  and  miscellaneous 4,513.04 

Expenses  of  Sewer  Commission,  engi- 
neering, land  damages,  superinten- 
dence       16,902.42 

3113,799.42 
Cost  per  foot  of  the  entire  system  . .  .  .81.18 


272  THE    SKPAKATli    SYSTEM    OF    SEWERAGE. 

The  ag"gTeg"ate  capacity  of  all  the  sub-systems  enumer- 
ated is  3,940,000  gfallons  of  sewag^e  proper  per  day.  Equal  to 
75  g-allons  per  diem  per  capita  for  a  population  of  52,530,  and 
at  the  same  time  a  capacity  to  discharg-e  about  2,000,000  g^al- 
lons  of  subsoil  water  per  day.  The  total  volume  on  this 
assumption  will  in  no  case  fill  the  sewer  more  than  71-100  of 
its  diameter  at  the  time  of  averag"e  maximum  daily  dis- 
charge. 

The  following-  is  a  schedule  of  bids  received  for  con- 
structing- a  system  of  sewers  in  Dayton,  Ohio: 


o 

in 

8 

o 

o 

•spjEA  3!qn3 

"? 

'I 

t 

■? 

'aiPPnd  't'^lD 

« 

■spjBA  ojqno 

vg 

O 

^ 

& 

o 

luaiusjuequig 

•snox  ui  aoud 

o 

o 

8 

N 

8 

8 

'gdij  uoji 

^ 

Iri 

00 

r^. 

o 

8 

8 

8 

8 

8 

X 

•M"EJ.-qsnij 

ui 

„■ 

ui 

ui 

oi 

O 

o 

o 

8 

■aiOH-<JuiBT 

M 

m 

rn 

Ol 

o\ 

o 

O 

8 

O 

o 

o 

o 

•aioH-UE;AI 

4- 

ui 

^ 

in 

"' 

'" 

" 

m 

N 

o 

V~l 

■auiAEda^ 

■* 

(-». 

"■ 

S 

8 

^ 

O 

w 

s 

„' 

N 

ri 

«■ 

« 

o 

O 

CI 

CO 

CO 

in 

en 

Ol 

o 

lO 

•^ 

o 

o 

O 

m 

in 

00 

•a- 

CM 

VO 

o 

O 

OV 

1^ 

VO 

H 

^ 

VO 

c^ 

o 

^ 

vo 

* 

in 

o 

o 

m 

CO 

o 

en 

o 

.^ 

vo 

w 

^ 

o 

o 

o 

u-1 

r^ 

o 

0 

p 

CO 

T*- 

m 

•"I 

N 

N 

a 

o 

00 

8 

o 

in 

t? 

J 

< 

a 

o 

8 

o 

„ 

»: 

CTi 

!j 

s 

O 

o 

o 

a 

r^ 

Cl. 

■^» 

m 

^ 

n 

N 

N 

CO 

vo 

fn 

u 

Q 

°. 

o 

J 

a 

9 

a. 

o 

O 

O 

"*■ 

a 

o 

f^ 

o 

« 

Z 

irt 

< 

a 

^ 

oo 

in 

N 

o 

c 

CO 

a 

u~t 

M 

C4 

^ 

vo 

"? 

'^. 

*^ 

"• 

la 

kn 

fn 

^ 

f^ 

00 

in 

tH 

M 

CO 

a 

u-> 

m 

M 

en 

Q 

oo 

< 

O 

O 

er, 

J 

'^ 

Id 

a. 

o 

(n 

en 

0 

0, 

*? 

* 

a 

lO 

N 

O 

m 

N 

• 

• 

. 

o 

I^ 

O 

vC 

vo 

t* 

5^ 

_: 

ifl 

BS 
H 
0 
0 

J! 

J3 

s 

C 

3 

n 
Ou 

u 

5 

o 

09 

C 

Bh 

c 

XI 

3 

1 

b 

a 

o 

K 

03 

274  THE    SEPARATE   SYSTEM    OF    SEWERAGE. 

This  system  is  still  in  process  of  construction.  The 
cost  of  construction  proper,  not  including"  the  expenses  of 
the  commission  for  land  damag^es,  eng^ineering"  and  other 
g-eneral  expenses  of  a  like  character  for  the  heavier  portion 
of  the  work  including"  main  sewers  that  are  intended  to  serve 
other  districts  is  as  follows: 

Brick  sewer,  42  inches  in  diameter,  1304  feet. 

40       "       "           "  30 

36       "       "          "  3380 

30       "       "          "  1809 

Pipe  sewer,    18       "       "  "  900 

12       "       "  "  624 

10       "       "  "  7853 

8       "       "  "         30478 

Man-Holes 135 

Flush-Tanks 45 

Lamp-Holes 166 

42-inch  iron  outlet 100  feet. 

Cost  of  construction  to  date $57,040.88 

Cost  per  foot  including"  man-holes,  flush-tanks, 

etc $1.25 

The  work  has  been  peculiarly  difficult  for  the  reason 
that  nearly  all  of  the  brick  sewer  has  been  laid  in  g"round 
below  the  level  of  the  river  at  times  and  it  has  been  neces- 
sary to  keep  a  steam  pump  in  operation  continuously  day 
and  nig-ht,  and  in  some  instances  two  of  them.  The  remain- 
ing" portion  of  the  work  is  much  less  difficult  and  the  sewers 
of  smaller  diameter,  being  mainly  laterals,  so  that  the  cost 
per  foot  of  the  entire  system  will  be  considerably  reduced. 

A  pumping"  station  has  been  constructed  capable  of 
handling"  20,000,000  g"allons  of  sewag"e  per  day  at  a  cost  of 
$6,562.26  for  the  building"  and  $5,810.00  for  the  machinery. 
This  will  add  about  $.19  per  lineal  foot  to  the  cost  of  that 


CHAP.    XII.  COST    AND    ASSESSMENTS.  275 

portion  of  the  system  which  it  is  proposed  to  construct  at 
present.  The  pumping-  station  will  ultimately  serve  a  much 
wider  territory  however. 

The  following-  Table  gives  in  a  condensed  form  valuable 
information  as  to  the  cost,  etc.,  of  thirty-five  sewerage  sys- 
tems. It  was  compiled  from  information  gathered  by  the 
Public  Improvement  Commission  of  Troy,  N.  Y.,  and 
appears  in  a  more  extended  form  in  the  Engineering  Record 
for  October,  1891: 


TABLE 

DATA    OF    COST    AND    CONSTRUCTION 


City. 


Akron,  O 

Alleghany,  Pa. 
Altoona,   Pa. . . 

Augusta 

Bloomington  . . 

Boston 

Buffalo 

Burlington,  Vt. 
Cambridge  . . . . 
Camden,  N.  J . 
Chicago 

Cincinnati 

Cohoes 

Council  Bluffs . 
Detroit 


Dubuque 

East  Saginaw.  . 

Elmira 

Erie 

Grand  Rapids. 
Kansas  City. .  . 

Kingston 

Lancaster 

Lawrence 

Lincoln. . . .    . . 

Little  Rock 

Milwaukee  .    .  . 

Newark . 

New  Haven  .  .  . 

Omaha 


Philadelphia. . 
Portland,  Me. 
Providence. . . 
Rochester. .  . 
Syracuse 


System. 


Combined 


j  Combined 

j  &  separate 

Combined  .  .  . 


Separate  . 
Combined 


Separate  . 
Combined 


Separate 


Combined 


6  rarely. 
0.25  to  0.6 


0.25 
0.2  . 


15 

0.25 

16 

5  • 
0.2  . 

25(?) 

0.5  . 


\  Combined   } 
I  &  separate  f 


Combined 


Per  Cent. 
Min.  Grade 
Pipe  Sewers. 


5 

8",  0.35 

24",  0.07 

0.24  . . . . 


0.33 

25(?) 


0.15 


0.4 


O.  I 


Sewage  per 

Cap.  Daily 

Gallons. 


70 


90 
60 


90 


60 

40 


50 
20 


o.  17 
0.22 
0.42 
0.25 


0.5 


0.25 


0.25 
0.25 


150 


80 


Cost  of 
Cleaning. 


$300  annually 
Nothing 


Nothing. 


$60  per  mile. 
$110  per  mile 


Nothing    .... 
$200  per  mile 

$13-56     " 
Nothing.  .... 
$10  per  mile. 


Nothing    .... 


$155  per  mile 


$19.98  pr  mile 
Nothing 


$37.98  pr  mile 
$64  50     " 
$1,000  ann'lly 
Nothing 


XXX. 

OF    THIRTY-FIVE    SEWERAGE    SYSTEMS. 


Cost  of  Pipe  Sewers. 

Cost  of  Brick  Sewers. 

Average 

Depth  of 

Sewers,  feet. 

8" 

10" 

12" 

15" 

18" 

24" 

30" 

36" 

48" 

60" 

$o   30 

$0  30 

$1  50 
I  50 

I  75 

$2  50 
2  25 

$2    50 
4  00 

3  00 
I  13 

$2  50 
4  50 
3  20 

1  82 

2  00 

3  75 
3  25 
3  67 

$g  00 

5  50 

6  70 

2  85 

5  00 
4  50 

4  00 

$9  00 

7  00 

4  09 

4  00 

8  00 

5  50 

9 
II  to  12 
10  to  12 

5  to  20 

10 
10 

gto2o 
10 

9 
8 

0  25 

0  35 

1  50 
I  00 

I  14 
0  gs 

0  38 

Q  60 

1  50 
I  00 
I  25 

1  14 

0  go 
0  gs 

2  00 

0  80 
0  54 

0  65 

0  70 

1  75 
I  20 

I  50 
I  50 
I  10 

1  07 

2  25 

0  go 
0  64 

0  70 

1  00 

2  00 

1  50 

2  15 
I  75 

I  50 

I  00 

0  82 

3  00 
2  00 

2  00 

3  50 

2  00 

3  70 
2  12 

1  30 

2  22 

4  00 

I  50 
3  25 

5  00 

3  00 

4  14 
7  50 

6  00 

g  00 

6  00 
5  20 
4  50 

1  40 

2  50 

I  25 
0  82 

1  70 
3  00 

2  10 
I  67 

I  50 

I  75 

0  75 
0  46 

13 

9 

6  to  8 

4-5 
10 

10  to  18 

10  to  12 

10 

8 

12 

9 

7 

7^  to  8 

8  to  12 

10 

io}i  to  I3>^ 

10 

loto  12 

12/2 

10  to  15 

7>^  tog 

II 

7  to  10 
10 

0  40 

I  82 

1  20 

2  65 

2  60 

0  65 

0  70 

0  80 

0  65 

1  10 
I  40 
I  25 
0  85 

I  00 

0  70 

I  30 
0  80 

I  60 

4  50 
4  00 

6  00 

2  25 

3  70 

4  20 

3  00 

0  go 

I  85 

3  05 

gin. 

I  00 
0  88 

I  40 

I  37 

2  45 

3  50 

3  90 

4  60 

0  77 

I  00 
4  40 

I  25 
4  90 
4  50 

I  50 
6  25 
5  60 

2  00 

10  00 

6  50 

0  40 

I  15 

0  45 

I  30 
0  60 

I  70 
0  75 

2  10 
I  00 

2  25 

1  55 

2  50 

1  55 

3  21 

2  75 
2  25 

2  54 

3  70 
2  50 
I  60 

I  25 

0  88 

1  2g 

0  go 

0 
1 .361 

1  48 
I  00 
0  70 

I  3ql   T  fit; 

3  10 

3  20 

4  28 

3  80 

2  25 

3  03 

4  33 

2  50 

3  65 
3  46 
5  83 

3  90 

2  25 

3  97 
5  05 
5  00 
3  25 

4  75 

5  63 
7  50 
4  00 

'"7'76 

6  41 

7  00 

6  55 

16  47 

g  80 

5  00 

8  36 

7  80 

0  55 

0  80 

I  12 
I  68 

1  10 

2  25 

2  39 

I  82 
I  25 

I  00 

1  36 

2  05 

1  40 

2  25 
1.865 

2  00 
I  50 
I  25 

0  70 

2  00 
0  64 

0  80 

t 
1 .036 

0  50 

0  40 

4  00 

7  60 

278 


THE    SEPARATE    SYSTEM    OF    SEWERAGE. 


The  Table  also  g-ives  valuable  information  as  to  the 
practice,  with  reference  to  g-rades,  cost  of  cleaning-  and 
depth  of  sewers  in  the  cities  mentioned. 

Examples  of  Cost  Computed  from  Time  Book. — Tables 
XXXI,  XXXII,  XXXIII  and  XXXIV  were  compiled  by  Mr. 
W.  E.  Ely.  They  were  computed  from  notes  taken  in 
actual  work,  and  represent  actual  cost  to  the  contractor. 
An  allowance  of  fifteen  to  twenty-five  per  cent,  above  these 
prices  would  be  proper  in  making-  preliminarj'  estimates  of 
cost.  The  soil  was  loam,  sand,  and  gravel,  and  the  roadway 
compacted  gravel.  The  trenches  were  sheet  piled  the 
entire  leng-th. 

TABLE   XXXI. 

ACTUAL    COST    OF    LABOR    AND    MATERIAL. 


-a  ^ 

- 

5  0 

- 

0 

0!    0 

0 

^  u 

.5  S 

V 

v 

XI  cu 

u 

(X 

3 

u 

a, 

"    6C 

g.s 

u  — 

6 

c 

■6 
a 

a. 

(*-( 

Oh 

H.C 

Oh 

<u 

O 

o 

0 

0  u 

c 

en 

bC 

a 

u 

J 

^J 

Zl 

^ 

<u 

(U 

Cu 

UJ 

01  CO 

E 

in 

■^^ 

u. 

H 

0 

0  ^ 

4) 

TO 

rt 

0 

C/3 

Q 

U 

u 

U 

0 

J 

C/3 

H 

as. 

as. 

as. 

as. 

as. 

as. 

C/.r. 

lo  inch. 

19 
29 

19 

1. 14 

1-55 
1. 14 

.60 
.87 
.60 

4 
5 
4 

lO       " 

Under  6>i  ft. 

29.92 

9.0 

63 

lO       " 

6}^  to  9  ft 

19 

36.82 

1. 14 

.60 

4 

II. 0 

72 

lO       " 

9     to  12  ft. 

19 

*57.68 

1. 14 

.60 

4 

15.5 

87 

lO 

12     to  15  ft. 

19 

46.70 

1. 14 

.60 

' 

12.6 

84 

*Considerable   water  was  encountered  at  this   depth,  which  accounts  for  the  increased 
cost  of  excavation. 


CHAP.    XII. 


COST  AND  assessmi<:nts. 


279 


Laborers'  wag"es,  $1.50  per  day;  superintendence,  $10.00 
per  day.  About  one-sixth  of  the  trenching-  was  in  water 
whose  averag"e  static  level  was  two  feet  above  the  g-rade  line. 
The  soil  was  of  averag"e  compactness.  The  trenches  were 
sheet  piled  nearly  the  entire  leng-th. 

TABLE  XXXII 

ACTUAL  COST  OF  LABOR  AND  MATERIAL. 


0 
0 

c  0 

cS    0 

i 

3 

o 

u 

0. 
a, 

.S  1) 

S.s 
1-  — 

6 

0 

B 
4J 

0 

'o 

N 

'o 

a 

Q 

Oh 

"o 

tn 

0 

u 

"^  -^ 
0  0 

.^^    nl 

en  CO 
0  ^ 

u 

c 
E 

4) 

u 

0 

be 

D 

< 

h 
0 

as. 

as. 

C/x. 

a.r. 

aj. 

as. 

C/j. 

6  inch. 

Under  6>^  ft. 

9 

15 

•54 

•  47 

3 

1-5 

29 

6     " 

6)4  to  9  ft. 

9 

21 

•54 

•47 

3 

4.0 

38 

6     " 

9    to  12  ft. 

9 

28 

•54 

•47 

3 

7.0 

48 

6     " 

12    to  15  ft. 

9 

*76 

•54 

•47 

3 

18.0 

107 

6     " 

15     to  18  ft. 

9 

60 

•54 

•47 

3 

30.0 

103 

8     " 

12 

•77 
.84 

1-55 

•58 
60 

3 
4 
5 

lO      ' ' 

19 
24 

12        " 

.87 

♦Considerable  water  was  encountered  at  this  depth,  which  accounts  for  the  increased 
cost  of  excavation. 

Laborers'  wag-es,  $1.50  per  day;  superintendence,  $10.00 
per  day.  Nearly  all  trenching-  was  dry.  The  soil  was 
rather  favorable  than  otherwise,  but  required  sheet  piling-. 


280 


THK   SKPARATE   SYSTEM    OF    SEWERAGE. 


TABLE  XXXIII. 


ACTUAL 

COST    OF 

LABOR 

AND     MATERIA 

L. 

-a  ^ 

_jj 

B  ° 

o 

nl   o 

u 

.5   aJ 

aj 

0) 

^  O- 

u 

6 

a- 

u 

a 

i.a 

D4 

c 

IK 

a 

Pi 

^ 

HE 

Cm 

«4-l 
O 

o 

'o 

a 
E 

CO 

'1-1 

ID 

J 
< 

N 

(U 

o 

v 

rt 

rt 

D 

0 

C/5 

Q 

u 

U 

U 

0 

h-J 

Cfi 

H 

as. 

Oj. 

C/^. 

0.r. 

Oj. 

a^. 

as. 

8  inch. 

Under  6'-^  ft. 

12 

35 

1. 1 

.58 

3 

9-83 

61 

8      " 

6)4  to  9  ft. 

12 

32 

I .  I 

.58 

3 

8.00 

56 

Laborers'  wag-es,  $1.50  per  day;  superintendence,  $10.00 
per  day.  Water  was  found  about  one-fourth  of  the  distance, 
but  did  not  seriously  retard  the  work.     The  soil  was  of  aver- 

ag"e  compactness. 

TABLE  XXXIV. 

ACTUAL    COST    OF    LABOR    AND    MATERIAL. 


T!  .^ 

• 

S  0 

0 

0 

?Pv- 

.5  S 

<u 

OJ 

.G    (^ 

^ 

a 

i^ 

(U 

d 

(U 

(U 

TJ 

a 

U 

a. 

a. 

a 

"o 

*j     TO 

a 

S 

■flD 
en 

00 

a 

►J 

< 

N 

<u 

0 

D 

rt 

3 

C/) 

Q 

U 

U 

U 

0 

J 

CO 

H 

as. 

as. 

as. 

as. 

a^. 

C/J. 

aj. 

12  inch. 

Under  6yi 

ft. 

26.25 

18.0 

3-45 

1. 16 

4.40 

II. 8 

65 

12 

6'/2  to  9 

ft. 

26.25 

27.5 

3-45 

1. 16 

4.40 

16.5 

79 

12 

9     to  12 

ft. 

26.25 

46.5 

3.45 

1. 16 

4.40 

16.5 

98 

12      " 

Over    12 

ft. 

26.25 

76.5 

3-45 

1. 16 

4.40 

29.5 

141 

CHAP.  XII. 


COST    AND    ASSESSMENTS. 


281 


Laboi-ers'  wagfes,  $1.50  per  day;  superintendence,  $10.00 
per  day.  Much  of  the  work  was  in  wet  trenches,  requiring- 
about  one  man  in  every  ten  at  the  pump.  In  some  of  the 
deep  trenching-  the  static  level  of  the  water  was  live  feet 
above  the  g-rade  line.  The  soil  was  tolerably  compact, 
except  where  water  was  found,  where  there  was  quicksand. 

Table  XXXV,  taken  from  the  Report  of  the  Bureau  of 
Sewers  of  Chicag-o,  1891,  shows  the  cost  of  the  sewers  built 
in  the  City  of  Chicag-o  in  ISDO.  These  sewers  are  on  the 
combined  plan. 

TABLE  XXXV. 

NEW  SEWERS  AND  CATCH  BASINS  BUILT  IN  CHICAGO  DURING  THE  YEAR   189O 
AND  COST  OF  SAME. 


Length. 

Size 

Average  Cut. 

Average 
Cost  per  foot. 

Amount. 

11,525 

9  inc: 

1.        10.3 

$0  98 

$11,294  50 

119,689 

12   " 

7-7 

I  06 

126,870  34 

114,503 

15   " 

8.1 

2  20 

137,403  60 

14,016 

18   " 

9.1 

I  47 

20,603  52 

4,400 

20   " 

10.8 

I  91 

8,404  00 

57.447 

2  fo 

ot.        9.2 

2  22 

127,532  34 

17.298 

2>^  ' 

10.9 

2  65 

45.839  70 

7.762 

3 

8.4 

3  50 

27,167  00 

5.942 

zY^  ' 

12.3 

3  86 

22,936  12 

2,705 

4 

6.5 

4  37 

11,820  85 

6,932 

4^  ' 

10.4 

5  00 

34,65o  00 

10,767 

5 

9-5 

4  41  + 

58,277  47 

2,623 

s'A  • 

14-5 

6  44 

16,892  12 

610 

6 

10. 0 

5  71 

3,483  10 

1,650 

7   ' 

12.5 

9  95 

16,417  50 

1.334 

JVz    ' 

lO.O 

9  35 

12,472  90 

379,203 

$682,075  06 

282 


THE   SEPARATE  SYSTEM    OF   SEWERAGE. 


Cost  of  2,986  catch-basins  built $119,440  00 

Cost  of  6,709  cubic  yards  of  rock  excavated.  .      23,483  00 


$142,923  00 
Total  for  sewers  and  catch-basins $824,998  06 

The  cost  of  the  entire  Combined  Sewerag"e  system  of 
the  City  of  Chicag^o,  up  to  and  including-  1890,  is  shown  by 
the  same  report  to  be  about  $2.65  per  foot.  The  system 
consists  of  about  784.737  miles,  of  which  360.694  miles  are 
constructed  of  brick  and  424.043  miles  of  vitrified  clay  pipe. 

From  the  annual  report  of  the  city  eng^ineer  of  Provi- 
dence, R.  I.,  1890,  it  appears  that  the  averag-e  contract  cost 
of  labor  per  foot  on  the  different  sizes  of  sewers  built  in 
Providence  during-  the  last  three  years  has  been  as  follows: 

8  inch  pipe  in  basin  connections $0  63 


12 
15 

16 

18 
20 
22 
24 
48 


"     sewer 1  20 

1  34. 

sing-le  course  brick  sewer 1  70 

2  05 

2  03 

1  50 

2  55 

3  25 


double 


20x30  inch  sing-le  course  brick  sewer 2  15 

22x33     "         "  "  "  "      2  60 

24x36     "         "  "  "  "      2  30 

26x39     "     double       "  "  "      2  60 

28x42     "         "  "  "  "      3  00 

36x54     "         "  "  "  "      2  65 

38x57     "         "  "  "  "      3  67 

40x60     "         "  "  "  "      5  47 

Rock  excavation  per  cubic  yard 4  00 

The  averag-e   cut   for   12  and  15  inch  pipe  sewers  was 
about  12  feet,   for  brick  sewers  13  and  15   feet,   with   the 


CHAP.    XII. 


COST    AND    ASSESSMENTS. 


:283 


exception  of  the  40x60  inch  sewers,  when  the  averag^e  cut 
was  about  24  feet.  The  excavation  was  mostly  in  sand  and 
gravel. 

Maintenance  of  Sewerage. — The  cost  of  cleaning"  and 
repairing  sewers,  the  cost  per  mile,  and  number  of  miles; 
also  the  number  of  catch  basins  and  man-hole  chambers 
distributed  in  the  three  divisions  of  the  City  of  Chicago, 
according-  to  the  report  of  1890,  is  as  follows: 


Divisions. 


Miles  of  Sewers. 


Nainber   of  Number  of  Man- 

Catch-Basins.  Hole  Chaml)ers. 


West 319.074 

South 312.246 

North 153.417 

Totals 784-737 


10.968 

10,041 

5,480 


26,489 


11.337 
12,258 

6.395 


29,990 


The  cost  of  repairing-  sewers  during-  the  year  was  Sl-t,- 
648.97,  being-  an  average  of  S18.67  per  mile. 

The  cost  of  cleaning-  was  $107,873.34,  making-  the  aver- 
ag-e  cost  $137.46  per  mile. 

The  total  cost  of  both  repairs  and  cleaning-  was  S122,- 
522.31,  an  averag-e  cost  of  S156.13  per  mile. 

Accounts,  as  found  in  the  reports  of  Sewer  Depart- 
ments, are  rarely  classified  so  that  the  cost  for  maintenance 
and  repairs  of  the  Separate  System  can  be  isolated.  The 
cost  of  maintenance  is  very  slig-ht,  however,  beings  confined 
almost  entirely  to  the  cost  of  an  inspector  who  has  the  care 
of  the  system  and  inspects  it  at  frequent  intervals. 

According-  to  the  report  of  the  Sewer  Commissioners  of 
Brockville,  Ont.,  the  yearly  cost  of  a  s^'stem  of  about  nine 
miles,  costing-  about  8100,000.00  is  S400.00,  S200.00  of  which 
is  for  repairs. 


284  THE   SEPARATE   SYSTEM    OF    SEWERAGE. 

The  cost  of  maintenance  of  forty-two  miles  of  sewers  on 
the  Separate  System,  in  Memphis,  in  1S89,  is  g-iven  as  fol- 
lows in  the  Eng-ineer's  report: 

MAINTENANCE. 

Repairing-  flush-tanks $1,648  55 

Repairing-  man-holes 43  02 

135  obstructions  removed 718  01^ 

Repairing-  streets 361  11 

Repairing-  damag-es 30  10 

Repairing-  sewers 127  81 

Cleaning-  sewers,  main 89  46 

Cleaning-  sewers,  laterals 93  20 

Tools,  etc 304  48 

Office  expenses 88  55 

Superintendent 1,200  00 

Miscellaneous 185  93 

$4,890  22^  ' 

Some  of  the  items,  particularly  $1,648  for  repairing- 
flush  tanks,  seem  to  be  larg-e  for  an  averag-e  year. 

Sewer  Assessments. — The  following-  are  some  of  the 
many  plans  adopted  for  assessing-  the  cost  of  sewers: 

1.  By  a  g-eneral  sewer  tax,  paying-  for  the  sewers  as 
fast  as  they  are  built. 

2.  By  issuing-  bonds  and  providing-  for  their  g-radual 
payment  by  a  g-eneral  tax. 

3.  By  assessing-  the  property  benefited. 

4.  By  paying  for  the  sewers  by  a  g-eneral  tax,  and 
charg-ing-  for  permits  to  connect  private  sewers. 

5.  By  assessing-  the  property  adjoining-  the  sewers  in 
proportion  to  the  frontag^e  of  each  lot. 

6.  By  assessing-  the  adjoining-  property  in  proportion  to 
the  area  of  each  lot. 


CHAP.    XII.  COST    AND    ASSESSESSMETS.  285 

7.  By  assessing-  the  adjoining  property  in  proportion  to 
the  value  of  each  lot. 

8.  By  assessing-  a  certain  part  of  the  cost  on  the  adjoin- 
ing property  in  proportion  to  the  frontage  (or  area,  or  value) 
and  raisings  the  remainder  by  a  general  tax. 

1>.  By  assessing-  a  certain  uniform  amount  per  foot 
front  on  adjoining  property  and  paying  the  remainder  bv  a 
g-eneral  tax. 

The  method  of  assessing-  the  cost  of  a  sewer  upon  "the 
property  benefited"  g-ives  rise  to  perplexing  questions. 
The  judg-ment  of  different  individuals  will  differ  widely  as 
to  the  limits  of  the  districts  benefited,  the  proportion  of 
benefit  derived  by  each  lot  owner  and  the  relative  value  of 
the  lots. 

In  assessing-  the  cost  of  sewers  in  any  section  on  the 
abutting  property  a  difficulty  arises  from  the  fact  that  some 
parts  of  an}'  system  will  be  much  more  expensiv^e  than 
others,  and  the  extra  cost  will  not  be  justly  charg-eable  to 
the  adjoining-  property. 

In  designing  any  system  of  sewers,  the  sewage  of  a 
whole  town,  and  the  convenience  of  all  the  citizens,  will 
require  the  construction  of  mains  costing-  from  two  to  four 
times  as  much  as  the  laterals,  and  the  conformation  of  the 
ground  may  necessitate  much  deeper  cuts  in  some  localities 
than  in  others.  To  compel  the  owners  of  the  lots  adjoining- 
the  mains  and  deep  cuts  to  pay  all  the  cost  of  them,  when 
the  extra  cost  is  incurred  to  benefit  distant  territory,  is  a 
manifest  injustice.  The  burden  of  the  expense  may  be 
more  nearly  equalized,  either  by  paying  for  the  whole  sys- 
tem by  a  g-eneral  tax  or  by  assessing  upon  the  lots  a  uniform 
amount  per  foot  front  (or  in  proportion  to  area,  etc.),  and 
paying  for  the  remainder  by  a  g-eneral  tax. 

To  charg-e  for  connecting-  private  sewers  with  the  public 
sewers,  more  than  a  nominal  fee  to  pa}^  for  inspection,  is  not 
advisable.     The  policy  should  be  to  encourage  the  citizens  to 


286  THE   SKPAKATE   SYSTEM    OF    SEWERAGE. 

use  the  sewers  and  abandon  the  objectionable  methods  for 
the  disposal  of  sewag"e  which  are  employed  where  sewers 
are  not  used. 

The  most  advisable  method  of  sewer  assessment  to 
adopt  in  an^^  place  will  depend  upon  the  conditions.  Among* 
the  most  important  considerations  are  the  following": 
Whether  the  whole  system  of  sewers  is  to  be  built  at  once  or 
by  piecemeal,  whether  there  is  to  be  one  outlet  or  several — 
that  is,  whether  there  are  distinct  sewer  districts,  the  cost 
of  the  sewers  and  the  financial  ability  of  the  citizens. 

It  is  evidently  impossible  by  any  of  the  above  methods 
to  distribute  the  cost  of  sewers  with  absolute  justice.  The 
method  of  general  taxation  discriminates  ag^ainst  outlying- 
propert}'  adjoining  which  no  sewers  are  built.  It  is  applica- 
ble to  districts  the  whole  of  which  are  tributary  to  one  sys- 
tem where  the  system  is  all  constructed  at  once  so  that  all 
property  is  benefited. 

The  method  of  assessing-  in  proportion  to  frontage  dis- 
criminates against  shallow  lots  and  vacant  property.  The 
method  of  assessing  according  to  area  discriminates  against 
deep  lots  and  vacant  areas. 

The  method  of  assessing  according  to  valuation,  espe- 
cially where  the  tax  is  all  spread  in  one  payment,  discrimi- 
nates against  improved  property  as  against  vacant  property 
which  ma}^  possibly  be  improved  the  following  year. 

According  to  information  gathered  by  Cambridge, 
Mass.,  it  appears  that  out  of  66  cities  13  paid  the  cost  of 
sewers  by  a  general  tax  and  53  assessed  benefits. 

Of  the  53  assessing  benefits,  14  assessed  the  whole  cost, 
15  assessed  three-fourths  of  the  cost,  10  assessed  three- 
fourths  of  the  cost  according  to  foot  frontage,  12  assessed 
one-half  to  three-fourths  the  cost  and  2  assessed  less  than 
one-half  the  cost. 

The  prevailing  rule  among  those  who  clearly  state  their 
practice  is  to  divide  the  cost  according  to  frontage. 


CHAP,    XII.  COST    AND    ASSESSMENTS.  287 

The  City  of  Providence  has  g'iven  considerable  attention 
to  this  question  and  assesses  according-  to  frontage  for  a  cer- 
tain depth  from  the  street,  and  for  a  certain  depth  farther 
assesses  according-  to  area. 

This  combination  of  the  methods  of  area  and  frontag-e 
tends  to  correct  and  equalize  the  discriminations  of  either 
method  used  sing-ly. 

Whatever  method  of  assessing-  benefits  be  adopted  there 
will  be  a  proportion  of  property  owners  that  will  be  dis- 
tressed if  the  whole  of  their  assessments  be  levied  for  collec- 
tion in  one  payment  as  is  almost  universally  the  custom  in 
the  United  States. 

In  many  cases  it  means  to  the  owners  of  such  property 
practically  a  forced  sale  of  the  property.  This  seems  to  be 
a  proper  field  for  the  application  of  the  principles  of  the 
Building-  and  Loan  Association,  or  in  other  words  a  massing- 
of  capital  and  an  association  of  interests  for  the  purpose  of 
distributing-  costs  over  a  series  of  3'ears  and  obtaining- 
money  in  comparatively  larg-e  amounts  at  corresponding-ly 
low  rates.  The  application  of  this  method  to  special  assess- 
ments, whichever  of  the  above  mentioned  methods  of  deter- 
mining- the  proportion  to  be  assessed  be  adopted,  is  not  at  all 
intricate  as  will  be  shown  later.  The  municipality  is  not 
less  interested  in  so  distributing-  the  cost  than  is  the  individ- 
ual. Statistics  show  that  a  very  small  proportion  of  cities 
"pay  as  they  g"o. "  Almost  without  exception  they  borrow 
in  large  amounts  on  long  time  and  usually  at  low  rates. 
This  is  unavoidable  in  a  wise  policy  of  public  improvements 
and  sound  finance.  Otherwise  public  works  would  necessa- 
rily be  constructed  piecemeal  at  a  greatly  increased  cost, 
and  a  great  loss  of  efficiency,  or  on  the  other  hand,  if  the 
proper  amount  of  capital  were  massed  at  one  time  for  the 
economical  and  efficient  construction  of  a  system  of  sewers, 
water  works  or  other  public  works  of  corresponding-  mag-ni- 
tude  the  variations  in  the  percentage  of  taxes  levied  from 


288  THK    SEPARATK   SYSTICM    OF    SEWERAGE. 

year  to  year  would  be  appalling-  and  undoubtedly  there 
would  be  an  exodus  of  the  population. 

Let  us  assume,  for  the  purpose  of  illustrating",  that  it  is 
proposed  to  construct  a  system  of  sewers  for  a  certain  dis- 
trict, which  is  entire  within  itself  (whether  converg^ing"  to  a 
sing-le  outlet  or  not  does  not  matter  so  long-  as  a  like  propor- 
tion of  the  cost  may  properly  be  distributed  equally  over  the 
territory  in  question).  Let  us  assume  also  that  the  cost  of 
the  system  complete,  including-  g-eneral  and  extraordinary 
expenses  is  $1.00  per  lineal  foot  and  that  private  property  is 
deemed  to  be  benefited  to  the  extent  of  $.40  per  lineal  foot 
on  the  frontag-e  plan  on  each  side  of  the  street  and  that  the 
balance  of  the  cost,  which  will  be  somewhat  in  excess  of  $.20 
per  lineal  foot,  by  reason  of  street  intersections  and  the 
rebates  which  it  will  be  necessary  to  allow  in  order  to  equal- 
ize the  assessments  on  corner  lots  and  triang-ular  pieces,  be 
borne  by  the  city.  We  will  assume  also  that  this  amount 
borne  by  the  municipality  is  equal  to  one-third  of  the -total 
cost  for  the  purpose  of  simplifying-  the  problem,  and  that  it 
is  desired  to  distribute  the  cost  of  the  sewers  over  the  term 
of  10  years,  principal  and  interest  to  be  met  b}'  10  equal, 
annual  payments. 

In  the  case  of  a  property  owner  having-  an  ordinary  lot 
of  50  feet  frontag-e  the  total  assessment  will  be  $20.00.  In 
Table  XXXVI  will  be  found  the  amount  of  equal  annual 
payments,  of  principal  and  interest  combined,  necessary  to 
cancel  a  loan  of  $100.00  at  various  rates,  and  maturing-  in  any 
number  of  years,  from  one  to  fifty. 


CHAP.    XII. 


COST    AND    ASSESSMENTS. 


289 


TABLE  XXXVI. 

INSTALLMENT  TABLE. 


Showing  the  amount  of  equal  annual  payments  (of  principal  and  interest 
combined)  necessary  to  cancel  a  loan  of  $ioo,  at  3,  3^,  4,  4^,  5,  6  and  7  per 
cent.,  payable  annually  and  maturing  in  any  number  of  years  from  i  to  50 


si 

<  a 

PER  CENT.  PER  ANNUM. 

< 

K  0 

CQ 

Z  X 

•03 

.03>4 

.04 

.04.^ 

.05 

.06 

.07 

I 

103. oco 

103.500 

104.000 

104.500 

105.000 

106.000 

107.000 

2 

52.261 

52.657 

53-020 

53.413 

53.780 

54-544 

55 • 309 

3 

35-362 

35-699 

36.026 

36.370 

36.726 

37.411 

38.105 

4 

26.903 

27.229 

27-550 

27-877 

28.202 

28.857 

29.5-^3 

5 

21.832 

22.147 

22.464 

22.778 

23.096 

23.741 

24.389 

6 

18.460 

18.771 

19.077 

19.386 

19.702 

20.337 

20.980 

7 

16.049 

16  353 

16.662 

16.969 

17.282 

17.914 

18.555 

8 

14.244 

14.548 

14.852 

15. 161 

15.472 

16. 103 

16.747 

9 

12.843 

13.145 

13-450 

13-757 

14.069 

14.702 

15.348 

10 

11.723 

12.024 

12.330 

12.637 

12.950 

13-5S6 

14.238 

II 

10.808 

11.109 

II .416 

11.725 

12.039 

12.679 

13.336 

12 

10  046 

10.348 

10.656 

10.966 

11.283 

11 .928 

12.590 

13 

9  403 

9.707 

10.014 

10.328 

10.646 

II .296 

11.965 

14 

S  853 

9-157 

9.467 

9  782 

10. 103 

10.759 

11.434 

15 

8.377 

8.683 

8.994 

9.311 

9-634 

10.296 

10.979 

16 

7.961 

8.268 

8.582 

8.902 

9-227 

9  895 

10.586 

17 

7-596 

7.904 

8.220 

8.542 

8.870 

9-544 

10.242 

18 

7.271 

7.580 

7.899 

8.224 

8-555 

9.236 

9.941 

19 

6.981 

7.294 

7.614 

7.941 

8.275 

8  962 

9.675 

20 

6.722 

7.036 

7.358 

7.688 

8.024 

8.718 

9-439 

21 

6.487 

6.804 

7.128 

7.460 

7.800 

8.500 

9.229 

22 

6-275 

6.593 

6.920 

7-255 

7  597 

8.305 

9.041 

23 

6.081 

6.402 

6.731 

7.068 

7-414 

8.128 

8.871 

24 

5-905 

6.227 

6.559 

6.899 

7.247 

7.968 

8.719 

25 

5  743 

6.058 

6.401 

6.744 

7.095 

7.823 

8.581 

26 

5-594 

5.921 

6.257 

6.602 

6.956 

7.690 

8.456 

27 

5  456 

5-785 

6.  124 

6.472 

6.829 

7-570 

S.343 

28 

5.329 

5.660 

6.001 

6.352 

6.712 

7-459 

8.239 

29 

5.212 

5.545 

5.888 

6.241 

6.605 

7.358 

8.145 

30 

5. 102 

5-437 

5  783 

6-139 

6.505 

7.265 

S.059 

(Table  concluded  on  next  Page.) 


290 


THE    SEPARATE   SYSTEM    OF    SEWEKAGIC. 


TABLE  XXXVI  CONTINUED. 


z  w 

PER  CENT. 

PER  ANNUM. 

OS  X 

<  w 

u 

^1 

K  O 

' 

5 

•03 

.03>^ 

.04 

■  04 'A 

-05 

.06 

.07 

31 

5.000 

5-337 

5.686 

6.044 

6.413 

7.179 

7.980 

32 

4-905 

5 

244 

5 

595 

5 

956 

6.328 

7. 100 

7 

907 

33 

4.816 

5 

157 

5 

510 

5 

875 

6.249 

7.027 

7 

841 

34 

4-732 

5 

076 

5 

432 

5 

798 

6.176 

6.960 

7 

780 

35 

4.654 

5 

000 

5 

358 

5 

727 

6. 107 

6.897 

7 

723 

36 

4.580 

4 

928 

5 

289 

5 

661 

6.043 

6.839 

7 

672 

37 

4-511 

4 

861 

5 

224 

5 

598 

5-984 

6.786 

7 

624 

38 

4.446 

4 

798 

5 

163 

5 

540 

5-928 

6.736 

7 

579 

39 

4.384 

4 

739 

5 

106 

5 

486 

5.876 

6.689 

7 

539 

40 

4.326 

4 

683 

5 

052 

5 

434 

5.828 

6.646 

7 

501 

41 

4.271 

4 

630 

5 

002 

5 

386 

5-782 

6.606 

7 

466 

42 

4.219 

4 

580 

4 

954 

5 

341 

5-739 

6.568 

7 

434 

43 

4.170 

4 

533 

4 

909 

5 

298 

5.699 

6.533 

7 

404 

44 

4-123 

4 

488 

4 

»66 

5 

258 

5.662 

6.501 

7 

376 

45 

4.078 

4 

445 

4 

826 

5 

220 

5.626 

6.470 

7 

350 

46 

4-037 

4 

405 

4 

788 

5 

184 

5-593 

6.442 

7 

326 

47 

3  -  996 

4 

367 

4 

752 

5 

151 

5-561 

6-415 

7 

304 

48 

3-958 

4 

331 

4 

718 

5 

119 

5-532 

6.  ^90 

7 

283 

49 

3.921 

4 

296 

4 

686 

5 

089 

5-504 

6.366 

7 

264 

50 

3  887 

4 

263 

4 

655 

5 

060 

5.478 

6.344 

7 

246 

Assume  that  the  municipality  can  obtain  money  at  four 
per  cent  for  the  time  stated.  From  the  table  we  ascertain 
that  a  loan  of  $20.00,  maturing-  in  ten  years  at  4  per  cent,  will 
be  canceled  by  10  equal  annual  payments  of  $2.46  each. 

If  it  be  assumed  that  the  cost  of  the  entire  improvement 
be  $150,000.00  and  the  ag-g^re^ate  amount  assessed  ag^ainst 
the  property  by  special  assessment  by  any  of  the  methods 
described  be  $100,000.00  and  the  amount  borne  by  the 
municipality  at  larg-e  be  $50,000.00  as  previously  stated,  we 
find  from  the  table  that  the  amount  to  be  borne  by  the  city 
at  larg-e  will  be  paid  by  10  equal  annual  payments  of  $6,- 
165.00,  which  is  the  amount  to  be  levied  by  g-eneral  tax  each 


CHAP.    XII.  COST    AND    ASSKSSMICNTS.  291 


year,  and  the  ag-greg-ate  of  the  special  assessments  ag-ainst 
the  property  frontage  will  be  $12,330  each  year. 

A  separate  account  should  of  course  be  kept  of  the  fund 
and  all  that  remains  to  be  done  is  to  add  the  several  amounts 
charged  against  each  property  (corresponding  to  the  $2.46  in 
the  case  cited)  to  the  yearly  assessment  of  the  property  and 
to  add  the  municipality's  proportion,  (corresponding-  to  $6,- 
165,00  in  the  case  cited)  to  the  amount  to  be  levied  in  the  g'en- 
eral  tax  roll  each  year  for  ten  years,  until  the  account  is 
closed.  The  clerical  work  in  this  method  is  not  more  than 
when  others  are  used. 

In  some  cases  loans  can  be  secured  at  a  lower  rate  on 
bonds  maturing  after  a  stated  number  of  years  and  bearing 
annual  interest.  Where  it  is  desirable  to  secure  funds  in 
this  manner  the  method  above  outlined  can  be  used  to  pro- 
vide a  sinking  fund  for  the  payment  of  these  bonds  at  matu- 
rity. 


CHAPTER  XIII. 

COMBINED  SEWERS. 

Under  some  circumstances  it  may  be  necessary  to  con- 
struct combined  sewers.  When  this  is  the  case  the  size  of 
the  sewers  is  determined  by  the  amount  of  storm  water  to 
be  provided  for.  The  volume  of  sewag"e  proper  is  so  small 
in  comparison  with  the  volume  of  the  storm  water  during" 
the  continuance  of  a  storm  that  the  sewage  need  not  be 
taken  into  consideration. 

In  determining-  the  size  of  "Combined  Sewers"  the  fol- 
lowing points  must  be  taken  into  consideration: 

1.  The  area  from  which  the  storm  water  is  to  be 
g^athered. 

2.  The  rate  of  rain-fall. 

3.  The  relative  proportion  of  the  roofed  and  paved  area 
to  the  whole  area  to  be  drained. 

4.  The  nature  of  the  soil  in  the  unpaved  part  of  the 
area. 

5.  The  amount  of  g^round  water. 

6.  The  natural  grade  of  the  surface. 

7.  The  available  grade  for  the  sewer. 

The  rate  of  rainfall  has  been  quite  g"enerally  determined 
in  those  sections  which  have  been  long-  enough  settled  to  feel 
the  necessity  for  sewers. 

It  is  evident  that  the  larg-er  the  proportion  of  the  roof 
and  paved  area  the  larger  will  be  the  percentage  of  the  rain- 
fall to  be  provided  for  by  the  sewers.  The  permeability  of 
the  soil  in  the  unpaved  areas  will  also  materially  effect  the 
proportion  of  rainfall  which  reaches  the  sewers. 

The  grade  of  the  surface  will  determine  the  rapidity 
with  which  the  storm  water  will  flow  to  the  sewer,  and  the 


CHAP.    XIII.  COMBINED    SEWERS.  293 

grade  of  the  sewer  will  determine  the  velocity  of  the  flow  of 
the  sewage,  and  hence  the  capacity  of  the  sewer  to  dispose 
of  the  gathered  storm  water. 

It  is  very  difficult  to  estimate  the  amount  of  ground 
water  to  be  provided  for.  In  some  cases  there  ma}'  be  con- 
siderable water  for  a  short  time  and  but  very  little  after- 
wards. 

Where  the  sewer  intercepts  a  water  bearing  stratum 
the  flow  may  be  not  only  considerable  but  constant. 

Sewers  are  rarely  built  large  enough  to  dispose  of  the 
most  rapid  falls  of  rain.  A  certain  depth  per  hour  is 
assumed  as  reaching  the  sewers  and  the  sewers  are 
designed  to  dispose  of  the  amount  of  water  falling  on  the 
sewered  area  at  the  assumed  rate  of  rainfall  over  the  whole 
surface. 

The  depth  of  rainfall  assumed  as  reaching  the  sewers 
varies  under  the  different  circumstances  from  half  an  inch 
to  one  inch  per  hour  and  even  more  in  some  cases.  In 
exceptional  cases  rain  has  fallen  at  four  or  five  times  that 
rate. 

Several  different  formulas  have  been  proposed  for  deter- 
mining the  size  of  storm  sewers.  The  following  are  some 
of  these: 

Julius  W.  Adams'  formulas.* 


-  \  1542. 


^=>|  15427/ [IJ 

in  which  Z>  =  diameter  of  sewer  in  feet. 

^=cubic  feet  per  second  to  be  provided  for. 

X  =  length  of  sewer. 

j^=rise  for  length  L. 

^     2  log.  .1+ log.  7V^— 3.79 
log.  /?  = ^ ^-^7^ [2] 

in  which  Z^  =  diameter,  in  feet,  of  sewer. 
.4=acres  to  be  drained. 
/V=  length  in  feet  in  which  the  sewer  falls  one  foot. 

*Sewers  and  drains  for  populous  districts,  pp.  47 — 68. 


294  THE    SEPARATE    SYSTH:M    OF    SEWERAGE. 

These  formulas  are  on  the  basis  of  one  inch  of  rain  per 
hour,  one-half  of  which  reaches  the  sewer  within  the  hour. 

Thomas  Hawksley's  Formula,  used  in  the  main  drain- 

ag"e  of  London:  • 

r        •     .•     •      u     N     3  1og-.  .4+iV+6.8      ,.„ 
log-,  diameter  of  mam  (m  mches)= — ■      [.ij 

^  =acres  drained. 

7\^=leng'th  in  which  the  sewer  falls  one  foot. 
This  is  on  the  basis  of  one  inch  of  rain  per  hour. 
Knowing"  the  amount  of  storm  water  to  be  provided  for, 
the  size  of  the  sewer  may  be  determine'd  by  the  formulas 
g"iven  in  a  former  chapter. 

The  Burkli-Zieg"ler  formula  for  the  probable  amount  of 
storm  water  is: 

^=1.25^r  J^ W 

^=  cubic  feet  of  water  per  acre  reaching-  the  sewers 

in  one  second. 
c—a.  coefficient  depending  upon   the  nature  of  the 

surface  and  varying-  from  0.25  in  rural  districts 

to  0.60  for  paved  streets,  averag-e  0.50. 
/-=  cubic   feet  of   water   per    second    falling   on   an 

acre, 
^'^the   number  of  feet  fall  of  the  surface  in  1000 

feet. 
^4=area  drained  in  acres. 

Forms  of  Sewers. — For  sewers  flowing-  half  full,  or 
more,  the  circular  section  is  best.  But  when,  as  is  usually 
the  case  with  combined  sewers,  the  ordinary  flow  of  sewag-e 
fills  but  a  very  small  part  of  the  cross-section  of  the  sewer, 
it  is  best  to  so  form  the  cross-section  as  to  concentrate  the 
stream  and  g-ive  it  more  depth.  The  form  usually  adopted 
is  eg-g-shaped  with  the  small  end  down. 


CHAP.    XIII.  COMBINED    SEWEKS.  29.5 

Materials. — Sewers  may  be  built  of  brick,  terra  cotta, 
stone  or  concrete,  or  a  combination  of  these  materials. 

They  are  usually  built  of  brick  laid  in  hydraulic  cement. 
The  bricks  should  be  burned  hard  and  laid  with  full  joints. 

Baldwin  Latham  g-ives  the  following-  formula  for  deter- 
mining" the  proper  thickness  of  brick  sew^ers: 

——-  =  thickness  of  brick-work  in  feet. 

f/=depth  of  excavation  in  feet. 

r=  external  diameter  of  sewer  in  feet. 

Catch  Basins. — The  storm  water  from  the  street  should 
be  first  received  in  a  "catch  basin,"  where  the  dirt  and 
debris  from  the  streets  can  settle  and  not  be  carried  into  the 
sewer.  They  are  usually  placed  at  the  street  corners,  near 
the  junction  of  the  g"utters. 

Man-Holes. — These  are  similar  to  those  on  the  separate 
sewers.  Plates  X  and  XVI.  They  start  from  the  spring-- 
ing  line  of  the  upper  arch  of  the  sewer. 

It  frequently  happens  that  storm  water  conduits  can  be 
built  separate  from  the  sewers  at  a  less  cost  than  to  build  a 
combined  sewer.  The  storm  water  conduit  need  not  be  as 
deep  as  a  sewer..  It  can  be  discharg-ed  into  the  nearest 
natural  water  course,  and  this  often  very  much  shortens  the 
necessary  leng-th  of  the  larg-e  conduit. 

Where  sewag"e  must  be  pumped  the  separation  of  the 
storm  water  from  the  sewag-e  is  a  necessity  if  economical 
workinof  is  desired. 


CHAPTER  XIV. 

SEWAGE  DISPOSAL. 

One  of  the  most  difficult  problems  presented  for  solu- 
tion to  the  Seinitary  Eng-ineer  to  day,  is  that  of  sevvag^e  dis- 
posal. How  to  effectually  dispose  of  the  solid  and  liquid 
wastes  in  any  community  so  that  they  will  be  neither  offen- 
sive or  dang-erous  to  any  one  is  a  question  of  g-rowing- 
importance.  The  rapid  increase  in  population  of  our  cities 
and  villag-es  swells  the  flood  of  sewag^e  which  is  poured  into 
the  streams,  polluting-  the  natural  sources  of  water  supply, 
while  the  demand  for  pure  water  is  of  necessity  rapidly 
increasing-. 

In  the  older  countries  of  Europe  the  pollution  of  water 
courses  by  sewag-e  has  forced  itself  upon  the  attention  of 
g-overnment  officials,  and  string-ent  laws  have  been  passed  to 
protect  the  purity  of  streams.  In  this  country  the  time  is 
not  far  distant  when  the  pollution  of  streams  and  lakes  by 
sewag-e  will  need  to  be  forbidden  by  law,  or  in  many  local- 
ities pure  drinking-  water  in  any  considerable  quantities  will 
not  be  obtainable. 

In  many  cases  there  is  no  available  outfall  for  the  sew- 
age and  the  question  of  its  disposal  comes  up  at  once  with 
the  inception  of  sewer  projects. 

Of  the  various  methods  of  sewag-e  disposal  those  which 
have  been  tested  on  any  considerable  scale  may  be  classed  as 
follows: 

1.  It  may  be  emptied  into  a  stream  or  large  body  of 
water. 

2.  It  may  first  be  clarified  by  straining-,  by  subsidence, 
by  filtration,  by  chemical  processes  or  by  a  combination  of 
these  and  the  effluent  turned  into  a  stream  or  bodv  of  water. 


CHAP.  XIV.  SICWAGIC    DISPOSAL.  2!>7 

,3.  It  may  be  applied  to  the  soil,  as  in  intermittent 
downwai'd  filtration,  broad  irrig-ation,  or  subsurface  irrig-a- 
tion. 

Dilution. — When  sewage  is  turned  into  a  stream  of  con- 
siderable size  the  disappearance  of  the  sewage  is  due  to  sev^- 
eral  causes.  The  sewagejs  diluted  by  the  large  amount  of 
water  into  which  it  is  discharged,  some  of  the  organic  mat- 
ter becomes  food  for  aquatic  plant  and  animal  life  and  some 
is  destroyed  by  oxidation,  and  the  remaining  solid  particles 
are  deposited  along  the  bed  and  banks  of  the  stream.  So 
long-  as  the  amount  of  sewage  is  small  in  comparison  with 
the  volume  of  water  this  method  may  be  admissible,  but  it 
is  in  use  in  scores  of  cases  where  it  ought  not  to  be. 

Rivers  and  lakes  often  become  so  polluted  by  sewag^e  as 
to  become  a  serious  menace  to  the  health  of  cities  on  their 
banks.  The  Chicago  River  and  Lake  Michigan  at  Chicago, 
and  the  Cuyahoga  River  and  Lake  Erie  at  Cleveland  are 
examples  of  this. 

Subsidence. — When  sewage  is  partly  purified  by  subsi- 
dence the  sewag-e  is  collected  in  tanks  and  allowed  to  stand 
until  the  solids  are  deposited  and  then  the  water  is  drawn 
off.  Although  somewhat  less  objectionable,  the  effluent 
water  is  charged  with  impurities  and  is  still  unfit  to  be 
turned  into  the  natural  water  courses. 

Filtration. — Filtration  is  sometimes  resorted  to  and  the 
sewage  is  passed  through  filters  of  various  sorts.  This  sep- 
arates more  of  the  solids  than  can  be  obtained  by  subsi- 
dence, but  the  effluent  is  still  unfit  to  be  turned  into  the 
streams. 

Chemical  Processes. — Chemical  processes  have  been 
extensively  used.  In  these  some  chemical  solution  is  mixed 
with  the  impounded  sewag-e,  which  precipitates  not  only  the 


298  THK    SEPARATE   SYSTEM    OF    SEWERAGE. 

solid  matter  but  also  a  part  of  the  substances  held  in  solu- 
tion. There  are  scores  of  these  patented  processes — too 
many  to  even  name  within  the  limits  of  this  chapter.  The 
solid  residuum  or  "sludg-e"  is  used  as  a  fertilizer.  The 
hope  that  the  "sludg-e"  would  be  of  g-reat  value  as  a  fertilizer 
has  not  been  realized  and  very  little  profit  can  usually  be 
obtained  from  this  source. 

The  effluent  water  is  far  from  pure  and  frequently 
decomposes  after  being-  turned  into  a  creek  or  river.  This 
method  mig-ht  be  used  advantag-eously  where  the  effluent 
passes  into  the  sea  or  larg-e  tidal  rivers,  where  the  water  is 
not  used  for  water  supply. 

Application  to  the  Soil. — Filtration  through  the  soil, 
both  upward  and  downward  has  been  used.  Intermittent 
downward  filtration  has  worked  quite  successfully.  By 
this  method  the  sewage  is  turned  on  to  g-round  which  has 
been  thoroughly  under  drained.  The  sewage  is  filtered  by 
passing-  throug-h  the  soil  and  much  of  the  organic  matter  is 
destroyed  by  oxidation  and  nitrification. 

Separate  filtering-  beds  are  prepared  so  that  they  may  be 
used  alternately.  The  effluent  water  is  quite  pure  if  the  fil- 
ter beds  are  properly  made  and  kept  in  g-ood  condition. 
The  amount  of  g-round  necessary  and  the  depth  of  the  under 
drains  depend  upon  the  character  of  the  soil. 

Where  sufficient  suitable  land  can  be  procured  broad 
irrigation  is  the  most  satisfactory  method  of  sewag-e  dis- 
posal. 

The  soil  should  be  loose  and  thoroug-hly  underdrained. 
Compact  clay  is  not  suitable  for  a  sewag-e  farm  without 
special  treatment  for  breaking-  up  and  loosening-  the  subsoil. 

The  amount  of  sewage  per  acre  which  can  be  disposed 
of  varies  with  the  nature  of  the  soil,  and  its  special  prepara- 
tion for  sewag-e  disposal.  In  practice  one  acre  of  land  has 
been  used  in  broad  irrigation  for  disposing-  of  the  sewag-e  of 
from  50  to  500  persons. 


CHAPTER  XV. 

THE    PURIFICATION    OF    SEWAGE    BY    APPLICA- 
TION   TO    THE    SOIL. 

It  is  still  an  open  question  whether  water  which  has 
been  contaminated  with  sewagfe  may  be  so  thoroug^hlv  puri- 
fied as  to  be  entirely  safe  for  culinary  uses. 

So  far  as  chemical  purification  is  concerned  there  is  no 
doubt  it  can  be  accomplished  by  filtration  throug^h  the  soil 
under  favorable  conditions.  Whether  the  effluent  can  be  so 
purified  by  this  means  as  to  contain  no  trace  of  the  bacteria 
which  are  supposed  to  incite  various  zymotic  diseases,  the 
water  having-  been  previously  contaminated  with  them,  is 
still  in  dispute  by  eminent  authorities  who  have  labored  in 
this  field.  It  is  well  known  that  the  purest  of  natural 
waters,  as  reg"ards  organic  matter,  are  those  which  have 
underg-one  prolong-ed  filtration  throug-h  the  soil.  Our  knowl- 
edg-e  of  the  causes  which  influence  the  purification  of  sewag^e 
when  applied  to  land,  either  in  broad  irrig-ation,  intermittent 
downward  filtration  or  subsurface  irrig-ation  is  rapidly 
extending-,  however,  and  this  is  a  field  of  such  promise  as  to 
justify  a  reference  more  at  leng-th  to  some  of  the  later 
achievements  and  conclusions  concerning-  this  method  of 
purification. 

The  impurities  with  which  sewag-e  is  charged  consist 
mainly  of  different  org-anic  compounds  in  various  stag-es  of 
decomposition.  It  is  not  practicable,  or  in  fact  desirable,  to 
prevent  the  decomposition  of  these  org-anic  compounds. 
With  the  exception  of  the  small  portion  which  may  be  con- 
sumed as  food  by  animal  life,  they  must  be  resolved  into 
their  elementary  substances  before  they  canag-ain  be  utilized 
by  plant  life  or  otherwise  rendered  innocuous.     It  is,  how- 


300  THE   SP:PAKATE    SYSTIiM    OF    SEWERAGE. 

ever,  practicable  to  so  control  the  conditions  of  decomposi- 
tion that  it  shall  become  inoffensive  and  the  resulting-  com- 
pounds shall  be  fixed  and  rendered  harmless  by  some  sur- 
rounding- medium.  The  soil  is  a  medium  which  not  only 
renders  these  products  innocuous  but  also  favors  a  mechan- 
ical separation  and  aeration  very  conducive  to  the  rapid  dis- 
integ-ration  and  absorption  of  the  putrescible  matters  con- 
tained in  the  sewag-e. 

In  the  report  of  the  Select  Committee  on  the  Metropolis 
Sewag-e  it  is  stated  that, 

"No  efficient  artificial  method  has  been  discovered  to  purify,  for  drinking 
and  culinary  purposes,  water  which  has  once  been  infected  by  town  sewage. 
By  no  known  mechanical  or  chemical  means  can  such  water  be  more  than  par- 
tially cleansed;  it  is  always  liable  to  putrefy  again.  Processes  of  filtering  and 
deodorization  cannot,  therefore,  be  relied  upon  to  do  more  than  mitigate  the 
evil.  Water  which  appears  perfectly  pure  to  the  eye  is  sufficient,  under 
certain  conditions,  to  breed  serious  epidemics  in  the  population  which  drinks 
it  Soils,  however,  and  the  roots  of  growing  plants  have  a  great  and  rapid 
power  of  abstracting  impurities  from  sewage  water  and  rendering  it  again 
innocuous  and  free  from  contamination." 

The  process  of  purification  of  sewag-e  by  filtration 
throug-h  the  soil  is  similar  to  that  of  burning-  up  or  oxidizing- 
the  org-anic  matter  leaving  only  a  harmless  mineral  residue, 
which  is  soluble  and  passes  off  in  the  effluent,  leaving-  the 
filtering-  medium,  when  properly  manag-ed,  undiminished  in 
efficiency.  The  application  of  sewag-e  intermittently  serves 
to  increase  the  amount  of  oxidation  similarly  to  opening-  the 
draft  of  a  furnace. 

The  chang-es  produced  by  wet  oxidation,  however,  are 
not  the  same  as  those  produced  by  heat,  there  being-  inter- 
mediate processes.  In  the  former  the  nitrog-en  of  the 
organic  matter  first  combines  with  the  hydrog-en  to  produce 
aminonia  which,  upon  uniting-  with  oxygen,  produces  nitric 
acid.  This,  in  turn,  combines  with  potash,  soda,  lime  or 
some  other  base  present  in  the  sewage  or  in  the  soil  to  pro- 
duce a  soluble  nitrate.      The  extent  to  which  this  sequence 


CHAP.  XV.  THIO    PUWII'ICATIOX    OK    SICWACrE.  301 

of  combinations  has  proceeded  is  a  measure  of  the  deg^ree  of 
purification  of  the  sewage.  The  larg-er  the  amount  of 
nitrates  in  the  effluent,  therefore,  and  the  smaller  the 
amount  of  ammonia,  the  more  completely  has  the  org-anic 
matter  of  the  sevvag"e  been  destroyed.  Later  investigations 
have  shown  that  the  earlier  of  these  processes  depend  on 
the  presence  of  living-  organisms. 

The  Influence  of  the  Bacteria  of  Nitrification. — The  fol- 
lowing interesting  facts  concerning  nitrification  or  the  con- 
version of  ammonia  and  the  nitrogen  of  organic  matter  into 
nitric  acid  in  the  soil,  upon  which  process  the  purification  of 
sewage  largely  depends,  were  given  by  Mr.  R.  Warrington, 
in  a  paper  read  before  the  Society  of  Arts  in  1882.* 

"Diluted  solutions  of  urine  or  of  ammonium  salts  containing  the  essential 
constituents  of  plant  food,  undergo  no  nitrification,  though  freely  exposed  to 
the  air,  if  only  they  have  been  previously  boiled  and  the  air  supplied  to  them  is 
filtered  through  cotton  wool.  If  to  such  sterilized  solutions  a  small  particle  of 
fresh  soil  is  added  no  action  at  first  appears  but  after  awhile  active  nitrification 
sets  in  and  the  ammonium  or  urea  is  convened  into  a  nitrate.  For  the  pro- 
duction of  nitric  acid  it  is  necessary  that  some  base  should  be  present  with 
which  the  nitric  acid  may  combine.  The  action  proceeds  best  in  the  dark. 
When  a  solution  has  thus  undergone  nitrification  a  drop  of  it  suffices  to  induce 
nitrification  in  another  solution,  which,  unless  thus  seeded  would  have  remained 
unchanged.  Boiling  the  soil,  or  the  solution  that  has  nitrified,  entirely  destroys 
its  power  of  causing  nitrification.  The  presence  of  antiseptics  also  prevents 
nitrification.  Lastly,  nitrification  is  confined  to  the  same  range  of  temperature 
which  limits  other  kinds  of  fermentation.  The  production  of  nitrates  proceeds 
very  slowly  near  the  freezing  point,  but  increases  in  rapidity  as  the  tempera- 
ture rises,  reaching  its  maximum  of  energy,  according  to  Schlaesing  and  Miintz, 
at  gg-  Fahr.  At  higher  temperatures  the  rate  of  nitrification  rapidly  dimin- 
ishes, it  almost  ceases,  according  to  the  same  observers,  at  122^  Fahr.,  and  at 
131-  Fahr,  no  change  occurs.  It  thus  appears  that  nitrification  can  only  be 
produced  in  the  presence  of  some  nitrified  or  nitrifying  material,  and  the 
whole  course  of  action  is  limited  to  the  conditions  suitable  for  the  activity  of  a 
living  ferment.  The  French  chemists  claim  to  have  isolated  the  ferment  by 
systematic  cultivation.      It  belongs  to  the  family  of  Baclciia. 


''The  Treatment  and  Utilization  of  Sewage — W.  H.  Coitield,  1S8-. 


302  THE    SEPARATE    SYSTEM    OF    SEWliKAGE. 

The  purifying  action  of  the  soil  on  sewage  is  probably  due  to  three  distinct 
actions:  i.  Simple  filtration,  or  the  separation  of  suspended  matter.  2.  The 
precipitation  and  retention  by  the  soil  of  ammonia  and  various  organic  sub- 
stances previously  in  solution,  3.  The  oxidation  of  ammonia  and  organic 
matter  by  the  agency  of  living  organisms 

The  last  mode  of  action  is  undoubtedly  the  most  important,  as  without 
oxidation  the  sewage  matter  must  accumulate  in  the  soil  and  the  filter  bed  lose 
its  efficacy.  The  filtering  power  of  a  soil  will  depend  entirely  on  its  mechan- 
ical condition.  The  precipitating  power  of  soil,  is  on  the  other  hand,  a  chem- 
ical function,  in  which  the  hydrated  ferric  oxide  and  alumina  and  the  silicates 
of  soils  probably  play  an  important  part.  The  oxidizing  power  of  a  soil  will 
depend  partly  on  its  mechanical,  partly  on  its  chemical  and  partly  on  its  bio- 
logical condition. 

It  was  formerly  supposed  that  the  oxidizing  power  of  a  soil  depended  solely 
on  its  porosity,  oxidation  being  assumed  to  occur  by  simple  contact  with  air  in 
the  pores  of  the  soil.  We  now  know  that  a  porous  medium  is  by  no  means 
essential  for  nitrification;  sewage  may,  indeed,  be  nitrified  in  a  glass  bottle,  or 
when  passing  over  polished  pebbles.  Though,  however,  porosity  is  by  no 
means  essential  to  the  nitrifying  power  of  a  soil,  it  is  undoubtedly  a  condition 
having  a  favorable  influence  on  the  rapidity  of  the  process;  a  porous  soil  of 
open  texture  will  present  an  immense  surface*  covered  with  oxidizing  organisms 
and  generally  well  supplied  with  air  requisite  for  the  discharge  of  their  functions. 
It  is  doubtless  owing  to  this  fact  that  nitrification  takes  place  with  so  much 
greater  rapidity  in  a  soil  than  in  a  liquid.  The  sewage  will  itself  supply  the 
substances  required   for   the  nourishment  of  the  oxidizing  organisms.      *     *     * 


*Iii  order  to  bring  out  the  po.int  here  spoken  of  by  Mr.  Warrington  a  little  more  promi- 
nently the  author  made  the  following  experiment,  which  may  be  of  interest: 

Fifty  cubic  centimeters  of  ordinary  screened  mason's  sand,  of  a  fineness  of  40  grains  per 
lineal  inch,  were  placed  in  a  chemist's  burette,  having  first  been  thoroughly  freed  from 
moisture  by  continued  drying  at  a  temperature  of  about  225°.  Water  was  then  introduced 
into  the  burette  from  below  by  aspiration,  so  as  to  facilitate  the  expulsion  of  contained  air 
until  the  voids  were  entirely  filled  and  the  amount  of  water  introduced  carefully  noted. 
The  burette  was  then  opened  below  and  the  excess  of  water  over  that  naturally  adhering  to 
the  particles  of  sand  was  allowed  to  drain  otf.  From  the  facts  noted  the  following  computa- 
tions were  made: 

The  total  air  space  in  the  dry  soil  was  36  per  cent,  of  the  cubic  contents.  The  water 
adhering  to  the  particles  of  soil  was  18  per  cent,  of  the  cubic  contents.  The  total  superficial 
area  of  the  particles  of  soil  for  each  cubic  foot  was  2,200  square  feet.  The  water  adhering  to 
the  particles  of  soil  for  each  foot  in  depth  was  equivalent  to  a  film  of  water  i-iooo  inches 
thick  and  2,200  square  feet  in  area.  Since  the  purifying  agencies  within  the  soil  and  its  con- 
tained air  have  been  proved  to  be  active  to  a  depth  of  at  least  three  feet  we  may  assume 
that  the  surface  of  sewage  which  is  exposed  to  the  action  of  these  purifying  agencies  is 
approximately  6,600  times  greater  when  sewage  is  applied  to  the  soil  intermittently  than 
when  it  is  simply  impounded  over  the  sams  area. 


CHAP.  XV.  THIC    PUKII'^ICATIOX    OF    SICWAGIC.  303 

*  *  The  organisms  which  effect  the  oxidation  of  organic  matter  are  abundantly 
present  in  surface  soils  but  are  probably  absent,  or  nearly  so,  in  subsoils.  In 
surface  soils  they  will  probably  be  abundant  in  proportion  to  the  richness  of 
the  soil  in  organic  matter.  Sewage  also  contains  the  organisms  necessary  for 
its  own  destruction,  and  under  fav^orable  conditions  these  may  be  so  cultivated 
as  to  effect  the  purpose." 

Later  investig-ations  concerning-  the  function  of  living- 
organisms  in  the  purification  of  sewage  lead  to  the  con- 
clusion that  they  increase  in  numbers  wonderfully  when 
sewage  is  applied  to  soil  originally  quite  deficient  in  organic 
matter,  the  conditions  thereby  beings  rendered  favorable  to 
their  increase  in  proportion  as  their  presence  becomes  need- 
ful to  the  purification  of  the  organic  substances  supplied. 
This  is  shown  in  the  experiments  of  the  Massachusetts 
Board  of  Health,  quotations  from  which  are  to  be  found 
farther  on. 

It  also  appears  from  experiments  carried  on  at  the 
model  farm  at  Rothamsted,  under  Messrs.  Lawes  &  Gilbert, 
and  elsewhere,  that  these  organisms  are  decidedly  more 
numerous  and  active  near  the  surface  of  the  g-round  and 
their  action  under  ordinar}'  conditions  is  said  to  cease  at  a 
depth  of  about  three  feet  and  to  be  very  uncertain  below  a 
depth  of  twelve  or  fifteen  inches. 

In  view  of  these  conclusions  it  appears  that  so  far  as  the 
action  of  these  organisms  is  concerned  it  is  unnecessary  to 
fjrepare  intermittent  filtration  beds  as  deep  as  was  formerly 
thought  advisable,  and  Dr.  Frankland  has  stated*  that 
whereas  in  the  Rivers'  Pollution  Report  he  had  recommended 
6  feet  depth  of  earth  for  intermittent  filtration  he  now  had 
reason  to  believe  that  two  feet  would  be  equall}'  effective. 

These  facts  are  also  substantiated  by  the  rapid  purifi- 
cation which  sewage  undergoes  when  supplied  to  the  soil 
immediately  below  the  surface  as  in  subsurface  irrigation. 

A  test  made  in  one  of  the  experimental  filtration  tanks 
of  the  Massachusetts  State  Board  of  Health,   to  determine 


*Van  Nostrand's  Engineering  Magazine,  November,  1886. 


304 


THE   SEPARATE    SYSTEM    OF    SEWERAGE. 


the  distribution  of  bacteria  at  different  depths  gave  the  fol- 
lowing- results: 

NUMBER    OF    BACTERIA    FOUND    IN    ONE    GRAMME    OF    SAND    AT    VARIOUS    DEPTHS. 


Distance  from 
Surface. 

May  22,  i88g. 

Distance  from 
Surface. 

May  22,  1889. 

o      to    ]A  inch 

1,760,000 

5  inches 

63,400 

Yz  to   K    " 

105  000 

8 

30,700 

i'4:toi>^    '■ 

207,200 

12        " 

34,100 

2  inches 

60,200 

19        " 

12,300 

3 

III,  300 

60 

4,  100 

The  most  rapid  decrease  is  in  the  upper  few  inches. 
Koch  says  that  the  micro  org^anisms  in  the  soils  he  has 
examined  diminish  rapidly  with  the  depth  and  at  the  depth 
of  a  metre  the  soil  is  nearly  free  from  bacteria. 

"It  has  been  found  that  if  one  starts  with  an  artificial  filter  bed  of  perfectly 
clean  sand,  containing  no  bacteria,  and  floods  it  with  dirty  water  the  water 
which  comes  through  for  the  first  few  days,  and  for  a  much  longer  time  if  the 
weather  be  cold,  will  be  but  little,  if  at  all,  purified.  Its  coarser  suspended 
particles  may  have  been  caught  in  the  sand  pores,  and  so  it  may  be  clearer, 
but  its  dissolved  organic  matter  and  its  bacteria  may  not  be  at  all  diminished. 
Indeed,  for  some  time,  strange  as  it  may  appear,  the  numbers  of  the  bacteria 
may  have  largely  increased.  In  fact,  it  appears  that  the  pores  of  such  a  fresh 
sand-filter  with  the  organic  matter  suspended  in  the  water,  form  a  most  excel- 
lent breeding  place  for  bacteria. 

This  seems  discouraging,  but  let  the  experiment  go  on,  and  after  a  while  if 
the  dirty  water  has  not  been  forced  through  the  sand  too  fast,  it  will  be  found 
that  the  number  of  living  germs  which  come  out  in  thfe  water  at  the  bottom  is 
growing  steadily  smaller  and  finally  the  water  may  be  nearly  or  quite  germ  free. 
Now,  if  the  chemist  exposes  some  of  the  filtered  water  to  his  delicate  tests  he 
may  find  that  the  organic  matter  which  was  in  solution  in  the  water  at  the  top 
has  already  diminished  or  entirely  disappeared,  being  represented,  perhaps,  by 
nitrogen,  which  has  formed  harmless  combinations  with  oxygen. 

It  really  seems  as  if  the  more  of  the  living,  growing  bacteria  you  had  in 
the  upper  layers  ot  your  filter  bed,   the  freer  became  the  water  below  both  in 


CHAP.  XV.  'iHi<:  PUKii'icA  riox  oi-  siowAC.i:.  805 


bacteria  and  organic  matter.  This  is,  in  fact,  the  case.  We  do  in  this  exper- 
iment what  nature  does  on  a  larger  scale — make  the  bacteria  fight  the  organic 
matter  and  themselves 

But  how  is  this  effect  produced?  The  bacteria  are  so  small  that  hundreds 
of  them  could  easily  pass  abreast  through  the  smallest  spaces  between  the  sand 
particles.     What  holds  them  back? 

When  the  sand  particles  at  the  upper  portion  of  these  filter  beds  have  been 
carefully  examined  it  has  bee*n  found  that  they  are,  after  a  few  days,  com- 
pletely encased  in  a  slimy  gelatine-like  envelope,  formed  of  a  material  which 
many  bacteria  secrete  around  themselves  as  they  grow  This  bacteria-formed 
slime  more  or  less  fills  the  pores  of  the  filter  bed,  enclosing  the  bacteria  them- 
selves and  the  sand  particles,  and  catches  and  holds  fast  on  its  sticky  surfaces 
not  only  suspended  matter  of  various  kinds  but  the  new  bacteria  which  come 
onto  the  filter  and  start  to  work  their  way  down  through  its  pores.  Here, 
many  of  them,  like  good  prisoners,  set  to  work  to  make  the  best  of  the  situa- 
tion, and  if  their  nature  permits,  turn  to  and  help  to  make  more  of  this  trap- 
slime  to  capture  the  next  comers. 

Many  of  the  enlarged  germs,  however,  do  not  form  this  material  and  these 
may  die  in  large  numbers  where  they  lie.  On  the  other  hand,  this  enforced 
detention  is  simply  paradise  for  many  of  the  germs.  Here  they  are  resting  at 
ease  in  a  slimy  confinement,  with  boundless  supplies  of  just  the  food  they  w-ant 
slowly  trickling  by  them.  The  food  is  dead  organic  matter,  which  the  average 
bacterium  simply  dotes  on  and  reeks  little  whether  it  be  in  solid  form  or  in 
solution,  so  there  be  enough  of  it.  At  it  he  goes  then,  and  by  some  wholly 
inscrutable  phase  of  the  life  power  in  his  tiny  body,  asunder  fall  the  atoms 
which  have  once  been  parts  of  animal  or  plant.  That  part  which  the  tiny  life 
spark  needs  to  keep  its  glow  agoing  is  appropriated.  The  rest  he  leaves,  its 
atomic  cravings  unsatisfied,  and  only  too  ready  to  succumb  to  the  wiles  of  the 
ever  amorous  oxygen,  which  must  always  be  present  in  a  perfectly  acting  filter 
bed. 

The  slowness  and  the  intermittent  character  of  natural  soil  filtration  is  a 
very  important  matter  in  the  accomplishment  of  perfect  results,  because  in  the 
times  between  rains  the  soil  pores  have  a  chance  to  become  filled  with  stores  of 
oxygen  in  the  form  of  ground  air. 

Behold  now  the  secret  of  this  marvelous  alembic  into  which  may  go  things 
most  foul  and  harmful,  but  out  of  which  comes  the  very  type  of  cleanliness — 
clear  spring  water.  It  is  largely  the  bacteria,  living,  growing,  multiplying, 
following  their  life  impulses  silently  and  unseen,  each  after  its  kind,  which, 
supported  by  the  active  agency  of  the  oxygen,  bring  about  this  beneficient 
result." — Pnidden,  in  Drinking  Water  and  Ice  Supplies. 


306  THE  sii:parate  system  of  sewerage. 

Nitrification. — 

"The  conditions  influencing  nitrification  have  been  for  the  most  part 
already  mentioned  incidentally.  We  may,  ho\^ver,  advantageously  recapitu- 
late them. 

"(a)  The  formation  of  nitrates  appears  to  require,  or  to  be  facilitated  by 
an  elei'aled  ieniperottire,  and  goes  on  most  rapidly  in  hot  weather  and  in  hot 
climates. 

"(/'I  According  to  Knop,  ammonia  that  has  been  absorbed  by  a  soil  suf- 
fers no  change  so  long  as  the  soil  is  dry,  but  when  the  soil  is  moistened  nitrifi- 
cation quickly  ensues.      Water  thus  appears  to  be  indispensable  in  this  process. 

"(<)  \n  alkali />ast' or  carbonate  a.^-peSirs  to  be  essential  for  the  nitric  acid 
to  combine  with.  It  has  been  thought  that  the  mere  presence  of  potash,  soda 
and  lime  favors  nitrification,  'disposes,'  as  is  said,  nitrogen  to  unite  with 
oxygen.  Boussingault  found,  however,  (Chii/iie  Agricole,  III,  igS)  that  caustic 
lime  developed  ammonia  from  the  organic  matters  of  his  garden  soil  without 
favoring  nitrification  as  much  as  pure  sand.  The  caustic  lime  by  its  chemical 
action,  in  fact,  opposed  nitrification,  while  pure  sand,  probably  by  dividing  the 
particles  of  earth  and  thus  perfecting  their  exposure  to  the  air,  facilitated  this 
process."* 

Absorptive  Power  of  the  Soil. — The  results  of  fifty-one 
experiments  bv  Dr.  Lissauer  to  determine  the  absorptive 
power  of  soils  point  to  the  following-  conclusions,  among- 
others: 

"(/)  The  liquid  entering  the  pores  of  the  soil  displaces  the  air  or  liquid 
previously  present,  forcing  the  former  upwards  into  the  atmosphere,  and  the 
latter  downwards  into  the  subsoil  or  effluent  water. 

"{2)  In  order  that  the  effluent  water  may  not  be  directly  polluted  by  the 
sewage  liquid,  the  maximum  supply  of  the  latter  must  not  be  more  than  can  be 
taken  up  b}^  the  pores  of  the  soil. 

"(j)  Drv,  loamy  soil  absorbs  more  than  peaty  soil  and  gives  up  less, 
whilst  dry,  sandy  soil,  on  the  contrary,  absorbs  less  and  gives  up  more.  Con- 
sequently a  loamy  soil,  though  it  absorbs  a  large  quantity  of  liquid,  can  seldom 
be  irrigated,  whereas  a  sandy  soil,  though  it  absorbs  but  little  may  often  be 
irrigated. 

"{4)  The  looser  the  soil  the  easier  water  courses  are  formed  in  it,  and 
therefore  the  less  can  its  maximum  power  of  absorption  be  approached,  other- 
wise the  sewage  liquid  might  penetrate  the  subsoil  before  the  whole  of  the 
ground  had  been  saturated. 


*Johnson — How  Crops  Feed. 


CHAP.    XV.  THIO    Pl'KIFICATIOX    Ol'    SIOWAGK.  307 

"(j)  In  order  therefore  that  the  effluent  water  may  be  protected  from 
pollution  it  is  especially  necessary  that  the  absorptive  power  of  the  soil  should 
be  known,  but  the  determination  is  of  no  value  unless  it  be  made  in  a  sample 
in  which  the  natural  position  of  the  particles  of  earth  has  been  undisturbed." 

The  Function  of  Nitrates. — It  should  be  stated  in  this 
connection  that  the  nitrates,  which  are  the  product  of  the 
nitrification  or  oxidation  of  the  or^^anic  matter  contained  in 
sewag^e,  supply  nitrog-en  in  its  most  available  form  as  plant 
food. 

"Experiments  in  artificial  soil  and  in  water  culture  show  not  only  that 
nitrates  supply  nitrogen  to  plants,  but  demonstrate  beyond  doubt  that  Ihey  alone 
are  a  sufficient  source  of  this  element,  and  that  no  other  compound  is  so  well 
adapted  as  nitric  acid  to  furnish  crops  with  nitrogen.  "* 

In  the  absence  of  plant  life,  a  portion  of  these  nitrates 
being-  verv  soluble,  passes  away  with  the  effluent  in  a  harm- 
less form. 

The  Committee  of  the  British  Association,  on  the  Treat- 
ment and  Utilization  of  Sewag-e,  made  an  estimate  of  the 
amount  of  nitrog-en  recovered  in  crops  on  Breton's  farm, 
near  Romford,  with  the  following-  results: 

"Of  everv  ico  parts  of  nitrogen  distributed  over  the  farm  during  the 
twelve  months,  10.67  parts,  or  about  one-tenth,  were  found  in  the  effluent 
water;  41.76  parts,  or  about  four-tenths,  were  recovered  in  the  crops,  making 
together  about  half;  and  47  57  parts  were  unaccounted  for  "f 

It  was  subsequently  ascertained  b}'  analysis  of  the  soil 
that  the  nitrogen  in  the  soil  had  largely  increased. 

Experiments  of  the  Massachusetts  State  Board  cf 
Health. — Bv  far  the  most  systematic  experiiuents  upon  the 
filtration  of  sewage  through  the  soil,  which  have  come  to  the 
knowledge  of  the  writer,  are  those  being-  conducted  by  the 
Mass.  State  Board  of  Health,  at  Lawrence,  Mass.  These 
experiments  have  been  conducted  so  carefully  and  thor- 
oughly and  over  such  a  wide  rang-e  of  conditions  that  they 

*Jobnson — How  Crops  Feed.  p.  90. 

tCortield,  on  the  Treatment  and  Utilization  of  Sewage,  p.  419. 


308  TH1<:   SEPAKATK    SYSTKM    OF    SKWKKAGE. 

are  of  particular  interest.  The  results  of  the  experiments 
are  contained  in  the  Report  of  the  Board  on  Purification  of 
Sewagfe  and  Water,  1890,  from  which  the  following-  informa- 
tion is  g-athered: 

"The  filtering  grounds  comprise  about  two-thirds  of  an  acre.  Upon  them 
are  ten  tanks,  circular  in  plan,  about  17  feet  in  diameter  and  allowing  for 
material  to  be  filled  in  5  feet  deep.  From  the  lowest  point  in  the  bottom  of 
each  tank  a  2-inch  pipe  conveys  the  drainage  to  a  flume  within  a  building, 
whence  the  effluent  is  taken  for  analysis  and  examination. 

The  tanks  were  filled  with  different  materials,  as  follows:  No.  i,  very 
coarse,  clean  mortar  sand;  No.  2,  very  fine,  nearly  white  sand;  No.  3,  peat; 
No.  4,  river  silt;  No.  5,  brown  garden  soil,  well  manured;  No.  6,  7  and  8  were 
filled  with  3  feet,  8  inches  of  coarse  and  fine  sand,  lo  inches,  of  yellow,  sandy 
loam  and  6  inches  of  brown  soil;  No.  9,  very  compact,  sandy,  hardpan  of  clay, 
sand  and  gravel,  covered  with  9  inches  of  brown  soil 

The  sewage  used  in  the  experiments  was  taken  from  a  main  sewer  draining 
a  portion  of  the  city.  Apparatus  was  erected  for  measuring  the  sewage  and 
the  effluent,  and  biological  and  chemical  analyses  of  both  were  made  daily. 
The  sewage  was  applied  intermittently  at  intervals  of  one  or  more  days." 

In  the  twentieth  Report  of  the  Board  we  find  the  follow- 
ing" statements  reg-arding-  the  g-eneral  results  which  have 
been  obtained. 

•'Sewage  can  be  much  more  efficiently  filtered  through  open  sand,  than 
through  sand  covered  with  soil.  Very  fine  material,  like  dust,  in  the  upper 
layers  of  a  filter,  prevents  free  access  of  air,  and  when  wet,  may  exclude  air  so 
completely  as  to  render  purification  impossible.  With  soil  or  sand  containing 
dust  at  the  surface,  periods  of  intermission  in  the  application  of  sewage  may  be 
made  so  long  that  the  surface,  becoming  dry,  may  allow  air  to  enter,  and  a 
high  degree  of  purification  may  result;  but  the  quantity  of  sewage  that  can 
thus  be  purified  is  very  much  less  than  when  the  upper  layers  of  the  filter  are 
composed  of  open  sand,  thrpugh  which  the  sewage  will  rapidly  disappear  and 
will  leave  room  for  air  to  enter  and  come  in  contact  with  the  thin  laminas  of 
liquid  covering  the  particles  of  Fand. 

The  experiments  of  last  winter  show  that  intermittent  filtration  can  be 
carried  on  upon  a  bed  of  coarse  sand  through  the  coldest  weather,  when  the 
beds  are  exposed  to  snow,  but  that  the  efficiency  of  the  beds  is  much  reduced 
by  such  exposure  and  the  consequently  low  temperature  of  the  sewage  passing 
through  the  sand.  Bv  protecting  the  beds  so  that  snow  cannot  fall  upon  them 
and  reduce  the  temperature  of  the  applied  sewage  to  near  the  freezmg  point, 
the  experience  of  the  present  winter  so  far,  indicates  that  very  complete  purifi- 


CHAP.     XV.  IIIIO    PUWll-ICA'ilON    Ol'    SICWAGE,  809 

cation  may  be  continued  through  very  cold  weather  by  applying  the  sewage 
intermittently  at  the  temperature  at  which  it  ordinarily  comes  from  the  sewer. 
The  experiments  of  last  winter  show  that,  when  the  beds  are  exposed  to  the 
snow,  intermittent  filtration  may  be  carried  on  through  the  moderate  weather 
of  winter,  alternated  .by  continuous  filtration  during  the  colder  period." 

"Four  tanks,  filled  with  clean  coar.se  mortar  sand  from  the  same  pit,  were 
subjected  to  different  conditions.  One  of  these  was  exposed  to  the  cold  and 
snow,  and,  although  it  received  sewage  daily  and  removed  about  two-thirds  of 
the  impurities  of  the  sewage  during  the  very  cold  months  of  January,  February 
and  March,  when  filtering  at  the  rate  of  30,000  gallons  per  acre  per  day,  it  is 
evident,  from  the  results  in  the  other  three  tanks,  which  were  not  expo.sed  to 
frost,  that  the  sewage  entered  and  passed  through  but  a  fractional  part  of  the 
area  of  this  tank,  and  the  result  is  as  poor  as  if  a  much  larger  quantity  had 
been  applied  to  a  like  area  not  obstructed  by  frost. 

The  three  other  tanks  were  supplied  with  sewage  at  the  rate,  respectively, 
of  30,000,  60,000  and  120,000  gallons  per  acre  per  day,  and  until  nitrification 
commenced,  in  the  latter  part  of  March,  periods  of  forty-one,  thirty-one  and 
twenty-seven  days,  respectively,  the  ammonias  indicated  that  97,  94  and  80  per 
cent,  of  the  impurities  of  the  sewage  were  removed. 

Nitrification  began  to  increase  in  all  of  these  tanks  between  March  lU  and 
30,  when  the  temperature  of  the  effluent  was  at  39O  or  40^.  In  the  course  of 
three  weeks  the  nitrates  had  increased  from  0,025  parts  in  100,000  to  o  250 
parts,  after  which  they  increased  much  more  rapidly,  and  nitrification  was 
most  complete  from  May  6  to  10,  or  six  weeks  after  it  began,  the  nitrates  then 
amounting  to  from  2.5  to  3.0  parts  per  100,000. 

During  the  increase  in  nitrification  the  ammonias  also  increased  for  a 
time,  and  became  nearly  one-third  of  those  of  the  sewage;  but  generally  before 
the  nitrification  reached  its  height  the  ammonias  decreased  rapidly,  until  they 
became  one-half  of  i  per  cent,  and  li  per  cent,  of  those  of  the  sewage.  The 
rapidity  of  purification,  as  shown  by  the  decrease  in  ammonias,  was  greatest  in 
the  tanks  which  had  received  the  most  sewage  and  had  the  greatest  amount  of 
nitrogenous  matter  stored  in  them  — the  effluent  from  the  sand  which  had 
received  the  least  sewage  being  more  than  a  month  later  in  reaching  its  condi- 
tion of  greatest  purification.  The  filter  receiving  sewage  at  the  rate  of  120,000 
gallons  per  acre  per  day  gave  an  effluent  for  three  months  after  purification, 
resulting  from  nitrification,  was  established,  in  which  the  ammonias  were  less 
than  lyi  per  cent,  of  those  of  the  sewage.  Upon  increasing  the  amount  filtered 
to  180,000  gallons  per  acre  per  day  the  ammonias  increased,  but  for  the  next 
four  months  averaged  less  than  2  per  cent  of  those  of  the  sewage. 

One  of  the  filters  receiving  sewage  at  the  rate  of  60, coo  gallons  per  acre 
per  day  for  seven  months  after  purification  was  established,  gave  an  effluent  of 
nearly  constant  quality,  having  one-half  of  one  per  cent,  of  the  ammonias  of 


310  THK    SEPARATE    SYSTEM    OF    SEWEKAGi:. 

the  sewage,  the  free  ammonia  averaging  0.0012  parts  and  the  albuminoid 
ammonia  0.0105  parts  in  100  000  parts,  showing  less  organic  matter  than  many 
of  the  drinking  waters  of  the  State. 

The  other  filter  of  the  same  material,  receiving  60,000  gallons  of  sewage 
per  acre  per  day,  gave  an  efHuent  for  three  months  after  purification  was  estab- 
lished, having  between  i  and  2  per  cent  of  the  ammonias  of  the  sewage,  but 
in  the  next  two  months  these  increased  to  6  and  then  to  10  per  cent.  This 
increase  was  due  in  part  to  the  imperfect  distribution  of  the  sewage  over  the 
whole  surface,  which  being  corrected,  the  percentage  of  the  ammonias 
decreased  and  averaged  for  December  4)^2  per  cent,  of  those  of  the  sewage 

The  tank  of  this  material,  which  has  filtered  at  the  rate  of  30,000  gallons 
per  acre  per  day,  was  as  stated,  a  month  later  than  the  others  in  reaching  an 
established  condition  after  nitrification  became  active.  For  the  following  six 
weeks  the  ammonias  of  the  efHuent  were  but  one  per  cent,  of  those  of  the 
sewage  and  the  nitrates  were  a  little  more  than  one  part  per  100,000  ' 

In  each  of  the  experiments  above  recorded  sewag^e  was 
applied  intermittently  at  intervals  of  one  or  more  days,  and 
disappeared  from  the  surface  in  a  few  minutes  or  in  a  few 
hours.  The  results  obtained  by  intermittent  downward  fil- 
ti'ation  in  the  above  experiments  are  very  favorable  and  in 
striking-  contrast  to  those  obtained  by  continuous  filtration 
as  will  be  seen  by  the  following"  extract  from  the  report. 
These  experiments  were  made  with  a  tank  wliich  received 
30,000  gallons  per  acre  per  day  in  the  experiments  on  intei*- 
mittent  liltration  and  through  the  same  material — coarse 
sand: 

"At  the  end  of  this  time  the  outlet  was  closed  and  the  tank  filled  with  sew- 
age, and  for  the  next  four  months  the  surface  of  the  sand  was  kept  covered 
with  sewage,  and  the  outlet  was  opened  each  day  sufficiently  to  allow  the  reg- 
ular quantitv  at  the  rate  of  30,000  gallons  per  acre  per  day  to  flow  out  The 
filter  was  thus  changed  from  the  condition  of  intermittent  filtration  to  that  of 
continuous  filtration.  During  the  first  month  the  nitrates  were  reduced  from 
one  part  per  100,000  to  less  than  o.oi  part,  at  which  they  continued  for  the 
remaining  three  months.  The  ammonias  rose  in  the  first  month  from  i  per 
cent,  to  iK  per  cent,  of  those  of  the  sewage.  In  the  second  month  they 
became  31  per  cent,  and  at  the  end  of  the  fourth  month  were  equal  to  those  of 
the  sewage. 

This  shows  distinctly  the  radical  difference  in  result  between  intermittent 
and  continuous  filtration.  In  intermittent  filtration  the  nitrification  was  active 
and,  as  shown  by  the  ammonias,   99  per  cent,   of  the  organic  impurities  were 


CHAP.   XV.  THK    PUHIl-ICA  riON    OF    SICWAGIO.  311 

removed,  while  in  continuous  filtration  the  nitrification  ceased,  and  the  same 
sand,  filtering  the  same  quantity  of  sewage,  stored  impurities  for  a  time,  but 
finally  poured  out  an  effluent  quite  as  impure  as  the  applied  sewage  " 

The  biolog-ical  analyses,  an  account  of  which  appeal's 
below,  are  also  of  particular  interest  as  furnishing-  an  index 
of  the  deg-ree  to  which  it  may  be  possible  to  free  sewage 
from  the  contamination  of  disease  g-erms  by  the  methods 
adopted,  and  also  as  corroborating-  the  statement  previously 
made  that  the  bacteria  of  nitrification  remain  in  the  upper 
strata  of  the  soil. 

•'From  these  open  sands  the  number  of  bacteria  in  the  effluent  has,  during 
the  past  six  months,  varied  from  2  per  cent,  to  a  very  small  fraction  of  i  per 
cent,  of  the  number  of  bacteria  in  the  sewage. 

A  filter  of  very  fine  sand,  after  filtering  an  amount  equivalent  to  8,600,000 
gallons  of  sewage  upon  an  acre,  filtered  at  the  rate  of  12, coo  gallons  per  sere 
per  day,  giving  an  effluent  in  which  the  organic  matter,  shown  by  the  loss  on 
ignition,  was  but  3  per  cent,  of  that  of  the  sewage,  and  the  nitrogenous  matter. 
as  shown  by  the  ammonias,  was  but  one-quarter  of  i  per  cent,  of  that  of  the 
sewage. 

The  loss  on  ignition  was 0.5000  parts  in  100.000 

The  free  ammonia 0.0002  parts  in  100,000 

The  albuminoid  ammonia  was 0.0062  parts  in  100,000 

The  nitrates  were. o  7000  parts  in  100  000 

At  the  same  time  the  bacteria  of  the  sewage  amounted  to  591,000  in  a 
cubic  centimeter,  while  those  of  the  same  quantity  of  effluent  amounted  to  2, 
and  these  may  have  come  from  the  air  while  collecting  the  sample.  By  both 
chemical  and  bacteriological  analysis  this  effluent  from  sewage  has  less  organic 
impurity  than  the  water  of  Lake  Winnipiseogee,  and  contains  but  little  more 
nitrogenous  organic  matter  than  city  water  filtered  through  the  same  material 
a  year  ago.  This  sand  stored  much  impurity  in  the  winter.  Nitrification 
began  actively  in  June,  and  for  three  months  appeared  to  be  active  in  removing 
stored  impurity,  so  that  purification  did  not  approach  the  completeness  given 
above  till  September,  since  which  time  it  has  steadily  grown  more  complete  " 

"Garden  soil  makes  a  very  poor  filter.  Upon  applying  sewage  intermit- 
tently to  a  body  of  garden  soil  five  feet  deep,  after  the  first  month  ths  organic 
impurities  increased  continually  for  eight  months,  until  the  effluent  became 
more  impure  than  the  applied  sewage.  There  had  then  been  applied  24,000 
gallons,  the  equivalent  of  4,800,000  gallons  on  an  acre,  and  it  was  then  being 
applied  at  the  rate  of  10,000  gallons  per  acre  per  day.  The  daily  quantity 
passing  through  has  since  been  reduced  to  5,000  gallons  per  acre  per  day,  and 


312  THE    SEPARATIC    SYSTEM    OF    SEWERAGE. 

the  quality  of  the  effluent  has  somewhat  improved,  but  still  contains  as  much 
nitrogenous  matter  as  crude  sewage. 

"A  very  few  vegetable  organisms  that  can  be  identified  by  the  microscope 
have  been  found  to  occasionally  pass  through  the  coarser  filters,  but  in  general 
none  come  through  A  few  animal  forms  have  been  found  in  the  effluent,  but 
these  may  grow  in  the  under  drains  and  outlet  pipe  The  question  remains  to 
be  settled,  whether  any  animal  or  vegetable  microscopic  organisms  live  to  get 
through  the  filters  of  finer  material  at  the  rate  which  sewage  has  been  filtering. 
Of  the  still  more  minute  organisms,  the  bacteria,  we  found  that  soon  after 
sewage  was  first  applied  to  the  tanks  they  came  through  in  great  numbers,  but 
became  reduced  in  number  and  during  the  later  winter  and  spring  months 
amounted  to  two  per  cent,  and  less  of  those  of  the  applied  sewage,  but  after 
nitrification  commenced  they  decreased  rapidly,  and  continued  through  the 
summer,  in  many  cases  less  than  one  hundred,  and  in  some  less  than  ten,  while 
the  number  in  the  same  quantity  of  applied  sewage  was  about  a  million." 

"The  experiments  made  to  the  present  time  show  that  the  number  of 
bacteria  in  the  sand  decrease  very  rapidly  from  the  surface  downward.  In  the 
finer  sands  they  nearly  or  quite  disappear  before  the  bottom  is  reached.  *  *  * 

We  have  reason  to  hope  that  filters  may  be  so  made  and  managed  that  all 
disease  germs  may  be,  with  certainty,  removed." 

The  Influence  of  Temperature. — Considerable  discus- 
sion has  arisen  as'to  the  practicability  of  sewag^e  disposal  by 
application  to  the  soil  during-  the  winter  months  in  northern 
latitudes. 

in  the  investig-ations  of  the  Massachusetts  State  Board 
of  Health  previously  quoted  it  was  determined  that: — 

"Durmg  the  cold  months  the  nitrification  was  about  nine-tenths  as  com- 
plete as  the  mean  for  the  year  and  that  the  loss  on  ignition  and  the  ammonias 
of  the  effluent  were  about  one-fifth  greater  percentage  of  the  amounts  in  the 
sewage  producing  the  effluent  than  for  the  year.  This  is  in  all  respects  a  very 
satisfactory  result  of  continued  purification  by  this  filter  (coarse  sand)  during 
the  winter." 

The  following'  abstract  from  the  report  of  the  Commit- 
tee of  the  British  Association  is  also  of  interest: 

"A  comparison  was  made  in  January,  1871,  during  severe  frost,  of  the 
results  obtained  in  the  purification  of  sewage  at  the  three  following  farms. — 
Breton's  farm,  near  Romford,  Biddington  farm,  Croyden,  and  Norwood  farm. 
It  was  found  that  in  the  latter  two  cases,  where  the  sewage  was  passed  over  the 
land  in  the  catch  water  system,  it  was  not  satisfactorily  purified,  the  nitrogen 
escaping  in  the  effluent  water  being  only  partially  in  the  state  of  nitrates  and 


CHAP.  XV.  I  HI';    PrKIl'ICATION    OK    SICWAGIC.  313 

nitrites;  while  at  Breton's  farm,  where  this  sewage  passes  through  the  soil,  the 
farm  being  in  effect  a  large  filter  bed  (i)  oxidation  goes  on  in  winter  as  well  as 
in  summer,  and  almost  all  nitrogen  lost  is  lost  in  an  oxidized  and  inoffensive 
form;  and  (2)  this  loss  is  very  slightly  greater  in  winter  with  a  very  strong 
sewage  than  in  summer  with  a  weaker  one."* 

"There  is  one  point  which  I  think  deserves  consideration  in  connection 
with  the  question  of  the  winter  disposal  of  sewage  upon  land,  and  this  is  the 
temperature  of  the  sewage.  *  *  *  *  While  it  is  probable  that  the  coldest 
sewage  may  be  disposed  of  upon  land  in  winter  in  this  climate,  such  disposal 
may  be  rnore  confidently  advised  where  the  sewage  is  warmer,  and  in  seeking 
for  precedents  it  is  desirable  to  know  the  temperature  of  the  sewage  as  well  as 
the  severity  of  the  winters. "f 

Aeration  of  the  Soil. — The  effects  of  a  lack  of  air  in  the 
interstices  of  the  soil  are  apparent  from  the  experiments  on 
continuous  filtration  previously  cited.  At  the  time  the 
experiments  were  in  prog"ress  the  outlet  pipe  from  the  tank 
was  trapped  so  that  no  air  could  enter  the  tank  from  below. 
There  is  reason  to  believe  that  the  lack  of  nitrification  in 
continuous  filtration  is  due  to  the  lack  of  oxygen.  In  order 
to  substantiate  this  fact  experiments  on  filtration  were  con- 
ducted at  the  experiment  station  at  Lawrence,  Mass.,  in  a 
tank  filled  with  coarse  sand  and  arrang-ed  so  that  the  quan- 
tity of  air  admitted  to  the  tank  could  be  controlled  by  an 
aspirator.  The  conditions  otherwise  were  the  same  as  in 
intermittent  filtration.  Sewage  was  applied  intermittently 
through  a  funnel  and  stop  cock  and  distributed  over  the  sur- 
face by  a  perforated  plate.  Nitrification  ceased  soon  after 
the  supply  of  air  was  stopped  and  the  effluent  was  little 
better  than  the  sewage.  Subsequently  the  cock  by  which 
sewage  was  admitted  to  the  tank  was  left  open,  thus  ventil- 
ating the  top  of  the  tank.  The  condition  of  the  effluent  did 
not  improve.  Upon  removing-  the  cover  of  the  tank  entirely 
the  condition  was  but  little  improved  by  reason  of  the  tank 
being  clogged  with  org^anic  matter  which  had  not  been  oxi- 


*Treatinent  and  Utilization  of  Sewage — W.  H.  Corfield,  p.  372. 
tF.  P.  Stearns  in  Transactions  of  the  Am.  Soc.  C.  E.,  January,  1888. 


314  THE    SlCPARATli    SYSTP:M    OF    SliWliRAGI': 


dized  diu"ing  the  time  that  the  air  was  excluded.  Upon 
removing-  half  an  inch  from  the  surface  of  the  tank  and 
applying-  an  aspirator  below,  drawing-  a  g-allon  of  air  each 
four  minutes,  the  effluent  rapidly  improved  and  in  two  weeks 
nitrification  became  complete.  During-  this  time  the  air  of 
the  tank  contained  almost  as  much  ox^^g-en  as  outside  air. 

"This  underground  air  is,  however,  almost  as  ceaselessly  in  motion  as  is 
that  in  which  we  move.  Whenever  the  ground  gets  heated  it  streams  out  of 
the  myriad  pores  of  the  surface  into  the  sunshine.  When  the  ground  cools, 
back  through  the  same  pores  rushes  the  aerial  air.  Every  wind  which  sweeps 
the  surface  moves  the  air  beneath  in  great  volumes.  With  every  rain  it  is 
driven  deeper  down.  The  movements  of  this  buried  atmosphere  are  slow, 
because  it  must  find  its  way  around  the  myriads  of  soil  particles  which  block 
its  course  But  it  is  of  great  extent  and  of  great  importance." — Priidden,  in 
Drinking  Water  and  Ice  Supplies,  iSgr . 

Effect  of  Different  Soils. — In  the  experiments  at  Law- 
rence it  was  found  that: — 

"With  the  gravels  and  sands,  from  the  coarsest  to  the  finest,  nitrification 
takes  place  in  all,  when  the  quantity  of  sewage  is  adapted  to  their  ability,  and 
the  surface  is  not  allowed  to  become  clogged  by  organic  matter  to  the  exclusion 
of  air.  With  fine  soils,  containing  in  addition  to  their  sand  grains,  two  or  three 
per  cent,  of  alumina  and  oxide  of  iron  and  manganese,  and  six  or  seven  per 
cent,  of  organic  matter  when  only  six  inches  in  depth,  resting  upon  fine,  sandy 
material,  they  retain  water  so  long  that  the  quantity  that  can  be  applied  is  so 
small,  and  the  interval  in  which  this  must  settle  and  dry  away  to  allow  air  to 
enter  the  filter  is  so  long,  that  the  amount  of  sewage  that  can  be  purified  is 
very  small.  When  the  quantity  applied  is  adapted  to  its  ability  such  a  filter 
may  give  an  excellent  effluent,  quite  free  from  bacteria." 

There  is  reason  to  believe  that  the  effect  of  simple 
mechanical  filtration  throug-h  the  soil  in  the  purification  of 
sewag-e  has  been  over-estimated. 

Where  compact  and  retentive  surface  soils  are  found  on 
a  more  open  subsoil  a  much  g-reater  quantity  of  sewag-e  can 
be  satisfactorily  purified  by  distributing-  it  beneath  the  sur- 
face throug-h  tile  drains  with  open  joints  as  in  subsurface 
irrig-ation.       The    application    in    this    manner   being-   more 


CHAP.  XV 


THK    PURIFICATION    OF    SI'JWAGi:. 


315 


favorable  to  the  admission  of  air  throug-h  the  comparatively 
impervious  surface,  especially  after  continued  use. 

In  one  of  the  experiments  at  Lawrence  the  capacity  of 
the  soil  to  purify  sewaf^e  was  increased  threefold  in  this 
manner. 

The  averag-e  results  of  purification,  at  Lawrence,  bv 
various  soils  for  periods  of  from  three  to  eig^ht  months, 
mostly  in  the  second  3'ear  of  filtration,  are  g-iven  in  the  fol- 
lowing- Table: 


CHAR.^CTER    OF    SOIL. 

0 
a. 

(D 

«    . 
<u  a 

=  1) 

C    '— 

—  0 

0 

Percentage  tlie  sum  of 
Ammonias  of  Effluent  was 
of  the  sum  of  Ammonias 
of  tlie  Sewage. 

Percentage  the  number  of 
Hacteria  in  tlie  Effluent 
was  of  the  number  in  tlie 
Sewage. 

Coarse  mortar  sand 

117.000 
60,000 
55,400 
42,600 
28,700 
13,400 

8.S80 

1-4 
0.4 

2.5 
0-5 
0.4 
0.6 

0.4 

3- 

0.02 

0. 19 

0.08 

0.003 

0.002 

O.OOI 

Coarse  and  fine  sand  and  fine  gravel. . 

Fine  white  sand 

River  silt,  mostly  fine  sand 

3  feet  8  inches  sand  and  gravel ) 

10  inches  yellow  sandy  loam - 

6         ' '       Brown  soil ) 

The  several  amounts  per  acre  of  sewag^e  set  opposite  the 
dijfferent  soils  are  the  amounts  the}"  were  found  by  experi- 
ment to  be  capable  of  purifying-  indefinitely. 

The  Table  exhibits  in  a  gfeneral  way  the  superiority  of 
the  more  open  soils  as  to  purifying"  larg-e  quantities  of  sew- 


316  THE   SEPAKATIC    SYSTEM    OF    SEWEKAGE. 

age   and   of   the   compact  and    more   finely    divided   soils   in 
removing"  living  organisms. 

Self  Purification  of  the  Soil. — Tank  No.  1,  in  the  experi- 
ments previously  quoted,  being  constantly  in  use  for  nearly 
two  years  without  any  renewal  of  material  or  removal  of 
sediment  from  the  surface  nitrified  much  more  completely 
during  the  latter  six  months  of  the  second  \'ear  than  during 
the  corresponding  months  of  the  first  year.  The  average 
percentag'e  the  nitrogen  of  the  nitrates  in  the  effluent  is  of 
the  total  nitrogen  in  the  sewage  being  for  1SS8,  4:4:  per  cent. 
and  for  1889,  65  per  cent.  It  thus  appears  that  the  effective- 
ness of  the  filter  considerably  increased.  The  quantity 
of  sewage  applied  in  each  period  varied  but  four  per  cent. 

The  facts  previously  cited  as  to  the  behavior  of  tank  No. 
1  upon  the  resumption  of  intermittent  filtration  after  a 
period  of  continuous  filtration  indicate  that  iuipurities  stored 
in  the  soil  when  the  conditions  are  unfavorable  for  purifica- 
tion are,  as  soon  as  the  proper  conditions  obtain,  rapidl}' 
removed  in  the  form  of  nitrates,  and  this  without  any  period 
of  rest. 

This  fact  is  of  particular  interest  as  effecting  the  dis- 
posal of  sewage  by  filtration  in  winter.  During  short  periods 
of  severe  winter  weather  the  surface  of  filtering  areas 
can  be  easily  kept  free  from  ice  by  the  continuous  applica- 
tion of  sewage,  which  may  be  followed,  as  the  weather 
moderates,  by  intermittent  applications.  The  soil,  storing 
in  an  inoffensive  form,  during  the  continuous  filtration  such 
impurities  as  cannot  be  oxidized,  and  subsequently  when  the 
conditions  for  intermittent  fiJtration  are  favorable  these 
stored  impurities  are  oxidized  and  removed  in  addition  to  the 
oxidation  of  the  sewage  applied  from  day  to  day. 

Experiments  with  intermittent  filtration  through  gravel 
stones  as  large  as  beans,  from  which  all  particles  of  soil 
and    sand    have   been   washed   out,    have   shown   that  when 


CHAP.  XV.  THIC    PURIFICATION    Ol'    SKWAGE.  317 

sewage  is  applied  at  the  rate  of  126,600  g-allons  per  acre  per 
day  for  a  period  of  three  months  98.5  per  cent,  of  the  org-anic 
matter  was  removed  and  the  stones  were  as  clean  as  at  the 
beg^inning". 

Practically  then,  it  may  be  said  that  the  soil  can  purify 
sewag"e  for  an  indefinite  time. 

It  is  said  that  sewag"e  has  been  applied  to  the  Craig"en- 
tinny  meadows,  near  Edinburg-h  for  the  last  200  years. 

Quantity  and  Concentration  of  Sewage. — From  the 
above  Table  and  the  conditions  essential  to  purification  it 
seems  fair  to  infer  that  the  capacity  of  a  soil  filter  to  remove 
a  certain  amount  of  org-anic  matter  from  sewag^e  depends 
upon  the  deg^ree  of  dilution.  For  instance,  if  the  org-anic 
wastes  from  each  person  be  mixed  with  26  g-allons  of  w^ater 
the  org-anic  matter  in  the  sewag-e  will  be  more  readily 
removed  than  if  mixed  with  100  g-allons.  The  deg-ree  of 
dilution  for  German,  Engflish  and  American  cities,  as  indi- 
cated by  the  statistics  of  water  consumption,  is  about  26,  35 
and  100  g-allons  respectively.  Excessive  dilution  must  seri- 
ously interfere  wnth  the  aeration  of  the  filter  upon  which  in 
a  larg-e  measure  depends  its  activity. 

In  like  manner  the  dilution  of  sewag-e  by  storm  water  is 
a  serious  objection  in  filtration  over  limited  areas  where  the 
application  should  be  reg-ular  and  substantially  uniform  in 
quantity. 

The  experiments  at  Lawrence  have  demonstrated 
that:— 

"The  preparation  required  to  render  filtering  areas  effective  appears  to  be 
the  introduction  by  the  sewage  of  the  particular  organisms  fitted  to  aid  in  this 
work,  and  their  accumulation  with  a  proper  food  supply,  and  other  favorable 
conditions  by  which  they  become  in  time  adapted  to  accomplish  the  most  com- 
plete purification  with  the  quantity  of  sewage  received.  Any  change  in  quan- 
tity or  mode  of  application  may  disorganize  this  working  colony  and  prevent 
the  best  results,  until  there  is  time  for  a  re-adjustment  adapted  to  the  new  con- 
ditions." 


318  THE   SEPARATE    SYSTEM    OF    SEWERAGE. 

Influence  of  Area. — In  the  purification  of  sewagfe  by 
intermittent  filtration  the  object  sought  is  ordinarily  the 
application  of  the  sewag'e  to  limited  areas  in  the  immediate 
vicinity  of  urban  districts,  where  the  value  of  land  practi- 
cally prohibits  its  application  over  areas  sufficiently  broad  to 
favor  its  utilization  in  ag"riculture.  In  broad  irrig^ation  and 
utilization  of  the  sewag'e,  the  areas  available  and  the  com- 
paratively small  quantity  of  the  effluent  make  the  process 
one  much  less  likely  to  be  disturbed  b}-  lack  of  proper  man- 
ag"ement. 

Experiments  made  at  Paris  upon  the  action  of  g-rowing- 
plants  upon  sewag'e  during-  irrig-ation  b}'  M.  Marie'-Davy 
g-ave  the  following-  results:  Out  of  a  supply  of  5,000  to  6,000 
cubic  meters  (tons)  per  hectare  (2.5  acres)  per  month,  only 
one-thirtieth  of  the  water  supplied  reached  the  subterranean 
drains.  Veg-etation  consequently  acts  as  a  powerful  upward 
drainag-e.  The  plants  absorb  the  useful  elements  of  the 
sewag-e  and  yield  to  the  atmosphere,  by  evaporation,  nearly 
the  whole  of  the  liquid  which  has  served  to  convey  them. 
Thus  purification  and  ag-riculture  utilization  perfect  each 
other. 

It  is  said  that  at  Dantzig-  during-  the  hardest  frost  the 
sewag-e  sinks  beneath  the  surface  coating-  of  ice  and  snow 
and  filters  throug-h  the  soil  without  causing-  any  injury  to  the 
plants  or  trouble  to  the  contractor. 

Sewage  Disposal  at  Pullman. — The  sewag-e  disposal 
works  at  Pullman  offer  a  g-ood  opportunity  for  observing- 
the  success  which  may  attend  intermittent  downward  filtra- 
tion in  northern  latitudes  under  somewhat  unfavorable  con- 
ditions. 

The  writer  made  a  somewhat  thoroug-h  examination  of 
these  disposal  works  during-  the  winter  of  1890-91  and  also 
chemical  analyses  of  the  crude  and  purified  sewag-e  with 
especial  reference  to  determining-  the  feasibility  of  disposing- 


CHAP.  XV,  THK    PURIFICATION    OF    SEWAGE.  319 

of  sewag'e  by  intermittent  downward  filtration  in  winter  in 
this  climate.* 

Pullman  is  sewered  by  the  Separate  System.  The  pop- 
ulation is  about  11,000,  the  sewag'e  from  dwelling's  averages 
from  120  to  130  g-allons  a  day  per  capita.  The  averag-e 
number  of  g"allons  of  sewag'e  pumped  per  day  in  1890  was 
1,800,000.  The  balance  of  the  sewag'e  being-  the  discharg-e 
from  factories  and  possibly  some  g-round  water. 

The  sewag'e  is  pumped  from  the  collecting-  well  throug'h 
a  twenty-inch  cast-iron  pipe  to  a  sewage  farm  about  three 
miles  south  of  the  city.  At  the  farm  end  of  this  pipe  the 
sewag'e  g'oes  into  a  receiving  tank  made  of  boiler  iron  which 
is  set  a  few  feet  above  the  surface  of  the  ground.  Throug'h 
the  center  of  this  tank  there  is  a  screen  in  an  oblique  posi- 
tion throug'h  the  meshes  of  which  substances  more  than  half 
an  inch  in  diameter  cannot  pass.  The  sewag'e  passes 
throug'h  this  screen  and  thence  into  the  distributing"  pipes. 

One  hundred  and  forty  acres  of  land  have  been  thor- 
oug'hl}"  piped  and  underdrained  for  the  reception  and  purifi- 
cation of  sewag'e.  Hydrants  are  placed  at  suitable  intervals 
so  that  the  distribution  can  be  conveniently  effected. 

Besides  the  area  devoted  to  broad  irrig'ation  there  are 
fifteen  filter  beds  having'  a  total  area  of  9>^  acres  speciall}^ 
prepared  for  intermittent  downward  filtration,  to  which  the 
sewag'e  is  applied  during'  a  considerable  portion  of  the  win- 
ter, and  whenever  it  cannot  conveniently  be  applied  to  the 
surface  under  broad  irrigation.  These  filter  beds  are 
underdrained  by  drains  12)^  feet  apart  which  converg'e  at  a 
man-hole. 

The  soil  of  the  filter  beds  and  of  the  entire  farm  is  the 
rich  alluvial  prairie  soil  underlaid  by  a  yellowish  clay  subsoil 


*I  am  indebted  to  Mr.  Duane  Doty,  Editor  of  the  Pullman  Journal,  Mr.  Cox,  Assistant 
Manager,  Mr.  C.  W.  Campbell,  Superintendent  of  the  sewage  farm,  and  Mr.  Chas.  H 
O'Neil.  Assistant  Engineer  of  the  sewage  pumping  station,  for  information  and  assistance. 


320  THE    SEPARATE    SYSTPIM    OF    SEWERAGE. 

and  poorly  adapted  for  purifying-  large  quantities  of  sewagfe, 
especially  when  the  temperature  is  low.  Nevertheless  the 
results  obtained  here  are  very  flattering. 

I  am  informed  that  it  is  usual  to  apply  the  sewage  of  one 
day  to  about  three  of  the  beds,  which  are  then  allowed  to 
rest  for  three  days  at  least.  About  half  of  the  filter  beds 
are  cropped  each  3'ear  with  quickly  maturing  crops,  such  as 
plants  to  be  transplanted.  While  the  crops  are  growing  no 
sewage  is  applied.  Plate  XXIX  is  reproduced  from  a  pho- 
tograph of  the  filter  beds  taken  at  the  time  the  examination 
was  made,  March  12th,  1891.  The  weather  had  been  severe 
for  about  ten  days  previous  and  the  temperature  at  7  a.  m. 
was  12°  above  zero.  The  beds  are  arranged,  on  ground 
slightly  inclined,  at  different  levels.  Sewage  is  admitted  to 
any  of  the  high  level  beds  at  will  through  gate  chambers,  one 
of  which  is  shown  in  the  foreground.  On  the  day  previous 
the  bed  at  the  right  was  flooded  with  sewage  to  the  depth  of 
about  10  inches.  This  had  nearly  all  disappeared  beneath 
the  surface,  a  thin  sheet  of  ice  one-fourth  to  one-half  inch 
thick  had  formed  on  the  impounded  sewage,  which,  as  the 
sewage  sank  beneath  the  surface  was  broken  into  small 
fragments.  There  is  no  accumulation  of  ice  which  inter- 
feres with  the  filtration  of  the  sewage.  The  temperature  of 
the  sewage  when  applied  to  the  beds,  as  taken  in  the  carrier 
after  being  conve3'ed  three  miles  underground  at  the  season 
when  the  subsurface  temperature  as  shown  by  observations 
is  about  at  its  lowest,  was  .51°  F.  The  temperature  of  the 
effluent  as  taken  in  the  man-hole  to  which  the  subsoil  drains 
converge  was  38°  F.  The  latent  heat  given  up  by  the  sew- 
age during  this  fall  in  temperature  quickly  melts  the  ice  that 
may  have  accumulated  on  the  filter  beds  and  the  sewage 
sinks  rapidly  beneath  the  surface. 

Experiments  previously  detailed  show  that  between 
these  temperatures  nitrification  is  comparatively  active. 


PLATE  XXIX. 


CHAP,  XV. 


THK    PUKIFICATIOX    OF    SICWAGK. 


323 


There  was  no  offensive  odor  at  the  beds,  with  the  excep- 
tion of  that  coming-  from  a  deposit  of  sludg-e  near  the  gate 
chamber,  and  this  did  not  extend  for  an}-  great  distance.  I 
am  informed  that  it  is  usual  to  keep  this  sludge  spaded 
beneath  the  surface.  The  surfaces  of  the  beds  are  occa- 
sionall}-  turned  over  with  a  plow  to  assist  in  keeping  them 
from  becoming  sodden  so  as  to  exclude  the  air. 

A  sample  of  the  crude  sewage  was  taken  at  the  end  of 
the  carrier  for  analysis  and  also  a  sample  of  the  purified 
effluent  was  taken  from  the  man-hole  to  which  the  tile  drains 
converge.  The  effluent  was  clear  and  sparkling  and  not 
unpleasant  to  the  taste.  The  Table  below  contains  the 
results  of  an  analysis  of  the  samples  collected  as  above 
stated. 

ANALYSIS    OF    CRUDE    AND    PURIFIED    SEWAGE    FROM    THE    PULLMAN    SEWAGE    FARM. 
(PARTS    PER    100,000.) 


Temperature 

Albuminoid  Ammonia 

Free  Ammonia 

Nitrogen  as  Nitrates 

Oxygen  required  to  oxidize  organic  matter 
Chlorine 


Crude  Sewage.       Plrified  Sewage. 


51-F. 

.60 

■30 

.41 
6.40 
4.20 


38 -F. 
.040 

•037 

.  180 

.760 

2. 100 


The  degree  to  which  the  purification  has  proceeded 
(assuming-  that  there  has  been  no  concentration  or  dilution 
of  sewage  from  evaporation,  subsoil  water  or  other  causes) 
is  indicated  by  the  following  Table: 

Albuminoid  Ammonia.    93^  per  cent. 

Free  Ammonia 88 

Nitrates 56 

Oxidizable  organic  matter 88 

Chlorine 50 

Total  Nitrogen  in  the  EfiSuent 21% 


324  THE    SEPARATE    SYSTEM    OF    SEWERAGE. 

Much  more  favorable  results  may  be  expected,  of 
course,  during-  the  warmer  weather.  The  intention  was  to 
ascertain  the  conditions  at  about  the  most  unfavorable  sea- 
son. As  previously  stated  the  soil  is  not  adapted  to  purify 
larg-e  quantities  of  sewag^e  having-  too  much  finely  divided 
org-anic  matter  in  its  upper  layers  which  interferes  with 
aeration  and  also  too  retentive  a  subsoil. 

Plate  XXX  is  reproduced  from  a  photog-raph  of  the  area 
devoted  to  broad  irrigation  and  crops.  Sewag-e  is  applied  to 
this  area  whenever  the  weather  in  spring  and  fall  is  favora- 
ble and  it  can  be  applied  without  interfering-  with  the  crops. 
In  g-eneral,  however,  no  sewag-e  is  applied  to  g-rowing-  crops. 
The  sewage  is  distributed  to  this  area  throug-h  a  system  of 
vitrified  pipes  having-  hydrants  at  convenient  intervals  from 
which  the  sewag-e  is  allowed  to  flow  over  the  surface  of  the 
ground.  Sewage  is  also  applied  to  meadow  lands  adjoining- 
this  area  in  the  spring. 

The  principal  crops  raised  upon  the  sewag-e  farm  are 
early  potatoes,  cabbag-es,  beets,  onions,  celery,  cauliflower, 
parsnips  and  squashes.  Mr.  Campbell,  the  superintendent, 
informs  me  that  the  g-ross  receipts  from  the  farm  (l-iO  acres) 
was  about  31:^,000  last  year. 

The  experiments  of  the  Massachusetts  State  Board  of 
Health  and  the  results  obtained  at  Pullman  under  conditions 
more  than  usually  unfavorable  indicate  that  the  disposal  and 
purification  of  sewag-e  on  land  in  this  climate  is  entirely 
practicable. 

The  following-  diagrams  have  been  a  convenience  to  the 
author  in  making-  estimates  and  are  added  here  with  the 
hope  that  others  may  possibly  find  them  so. 

They  are  compiled  from  computations  but  have  been 
tested  by  actual  account  of  materials  used  in  construction 
and  found  to  agree  well  with  averag-e  construction. 

The  amounts  of  masonry  and  mortar  g-iven  include  plas- 
tering for  the  exterior  of  the  sewer. 


PLATE  XXX. 


\:j' 


tn\m}memmt^^mm^^^ 


eLtMftWTi 

■     ■y-oT'-A'T  «  -         .  .. 


<3r«>vd  -?''*'<<■>-',      ^    -7-7  ydoc    O  J 


•     Jrp"^TA'^  

jTcrJ^i.^/t/'^BS/^   or^i^rc'<a    rfE^i/ii^o 


•<J^F^^■:l--|"^'rT-^:i^CffiUU^ 


jt)m.-^TrT4:tiii|^ttt4i-^ij:4i^j-tTti^mH+i+t+iiai4J^umi;^itm^^ 


n 


Plan  of  the  New  Trunk  and  Intercepting  Sewers  in  the  City  of  Washington 


harge  into  a  delivery  manifold  conduit  which 
:ads  to  the  siphon  chamber  adjacent  to  the  boiler 
oom,  a  i6  X  22  X  40-ft.  concrete-lined  steel-plate 
ink,  from  which  the  6o-in.  cast-iron  siphons  pass 
ut  under  the  river  to  the  outfall  sewer  on  the 
pposite  shore.  By-passes  are  provided  for  both 
lie  sediment  chamber  and  the  siphons,  so  that 
he  sewage  pumps  may  draw  directly  from  the 
ewer  connections  in  case  the  sediment  chamber  is 
ut  of  service  for  cleaning,  and  also  discharge  di- 
ect  to  the  eastern  branch  of  the  river  if  the  out- 
all  sewer  is  cut  out  for  repairs. 

The  separate  system  deep-service  sewer  which 
s  not  arranged  to  pass  its  flow  through  the  sedi- 
ment chamber  in  order  to  maintain  a  fixed 
lydraulic  gradient,  leads  to  a  pair  of  class  II 
•umps,  which  are  connected  to  discharge  into  the 
iphon  chamber  emptying  into  the  outfall,  or  to  a 
eparate  emergency  30-in.  by-pass  outside  of  the 
luilding  discharging  direct  to  the  river.  The  suc- 
ion  conduit  back  of  these  pumps  has  a  chamber 
vith  two  screens  in  series.  There  is  also  a  cross- 
onnection  with  hydraulic  gate  control  between 
his  suction  line  and  that  to  the  class  I,  which 
)ermit  the  pumps  in  either  class  to  take  care  of 
he  work  of  the  opposite  class  temporarily,  when 
lecessary.  This  is  of  great  value  in  maintenance 
md  also  permits  economically  loading  the  diflfer- 
•nt  units. 

Each  of  the  storm-water  pumps  draws  through 
n  independent  connection  from  the  storm  water 
hamber,  and  discharges  through  the  15-ft.  storm- 
vater  conduit  to  the  river.  The  floor  of  this  D- 
hape  conduit  is  below  low  tide  so  as  to  minimize 
he  ordinary  left  and  its  crown  is  level  with  ex- 
reme  high  water.  These  pumps,  of  which  there 
ire  eight,  are  identical  in  type  and  design,  and 
vhile  capable  of  lifting  their  rated  capacity  the 
naximum  height  of  15   ft.,  are  particularly  effec- 


the  National  (Jity  Bank,  ihe  ongmal  walls  wei 
left  standing,  while  the  interior  of  the  buildir 
was  completely  torn  out,  leaving  nothing  with: 
the  hollow  square  formed  by  the  walls.  It  w« 
decided  by  the  general  contractor,  the  Geo.  I 
Fuller  Co.,  instead  of  bracing  the  wall  by  heav 
diagonal  struts,  to  drive  sheet  piling  about  12  i 
inside  the  wall  footings  around  the  entire  ar( 
so  as  to  retain  the  earth  undisturbed  under  tl 
footings  and  thus  prevent  settlement.  A  contra< 
for  this  work  was  entered  into  with  the  Wen 
linger  Steel  Piling  Co.,  and  a  description  of  tt 
methods  appeared  in  The  Engineering  Recor 
for  July  4,  1908.  The  piling  company  was  ii 
formed  by  the  general  contractor  that  its  agrei 
ment  with  the  labor  organizations  required  th; 
shorers  at  $3.50  per  day  be  employed  for  th 
class  of  work,  the  contention  being,  evident! 
that  piling  was  essentially  shoring,  since  it  pei 
formed  the  same  office.  Were  it  not  for  th 
agreement  it  would  have  been  possible  to  us 
ordinary  labor  for  part  of  the  work  at  a  cost  c 
about  $1.75  a  day. 

The  second  instance  -was  in  connection  wit 
the  work  of  the  Crawford  Co.,  contractors  o 
the  Bridge  Loop  Subway.  The  New  York  Stal 
Commissioner  of  Labor  entered  a  complaint  wit 
the  Public  Service  Commission,  alleging  that  th 
Crawford  Co.  was  employing  men  to  do  shorer 
work  and  not  paying  shorers'  wages,  the  matti 
coming  under  the  commissioner's  jurisdiction  b 
cause  the  State  law  requires  that  the  prevailir 
rate  of  wages  be  paid  on  public  works.  When  tl 
hearing  was  held  before  Commissioner  Eustis  « 
the  Public  Service  Commission,  it  was  show 
that  the  men  in  question  were  engaged  in  diggii 
pits  and  were  placing  concrete  piles  for  rei; 
forcing  the  foundations  of  buildings.  Testimoij 
was    presented    by    the    contractor's    attorneys 


ADVERTISEMENTS. 


fslATIONAL 


Sewer   Pipe,  Culvert   Pipe,    Building 
Blocks,  Wall  Coping,  Tile* 


WE  HAVE  A  FULL  ASSORTMENT  OF  PIPE 
AND  FITTINGS  OF  SUPERIOR  QUALITY, 
ORDERS     FILLED      ON      DAY       RECEIVED. 


Prompt   Attention  to   Orders, 
Large  or  Small. 


THe   NATIONAL 
SEWER   PIPE  CO., 

BARBERTON,  O. 

Postal  and  Western  Union  Wires  in  Office, 
Long  Distance  Phone,  Akron  101. 
7  a.  m.  to  9  p,  m. 


Blackmer  &  Post  Pipe  Co., 

rianufacturers   of 

Vitrified 
Pipe 


BOTH 


STANDARD  AND  DOUBLE  SlRENQTH. 


Large  Sizes     \     |J  S; 
A  Specialty.      ^     |3  inch. 


A    desirable   and   economical   substitute   for 
Brick    Sewers     of    corresponding     capacity. 

Write  for  Prices   Delivered  at   Destination. 

BLACKMER  &  POST  PIPE  CO. 

ST.  LOUIS.  MO. 

Send  for  Pamphlet   "Vitrified  Pipe  vs.  Brick  Sewers. 


Pacific  Fiusn  Tank  GoiiiDanu, 

84  LaSalle  St.,  GtllCflGO,  ILL., 

Manufacturers  of 

TI16  Miller  fluiomaiiG  SiDlion, 

m  INTERMITTENT  FLUSH  TANKS. 


Used  tor 

Flushing 

Sewers 

and  for 

Subsoil 

Irrigation^ 

No  Moving 
Farts. 

No  Joints^ 

No  Little 
Traps. 


Received  the  ilighest  Award  in  its  Class  at 
the  World's  Columbian  Exposition  for 

Simpricltu  01  GonstruGlion,  Eftectiveness  and  ReHaDilitii 

SEND  FOR  ILLUSTRATED    CflTflLOGUE. 


The  Shone  Hydro-Pneumatic  System  of  Sewerage. 


The  Shone  System  has  been  in  operation  for  the  last  eighteen  years,  and 
has  been  successfully  applied  in  more  than  two  hundred  instances.  In  this 
country,  it  is  in  operation  at  the  following  cities:  Chicago,  111. ;  Winona,  Minn.; 
Fairhaven,  Mass.;  Lynn,  Mass.;  Worcester,  Mass;  Ithaca,  N.  Y.;  White 
Plains,  N.  Y.;  Charleston.  S.  C;  Portsmouth,  Va  and  Far  Rockawav,  L.  I. 
Shone  Ejectors  are  also  employed  to  discharge  the  liquid  refuse  from  seventy 
large  buildings  throughout  the  country,  from  which  a  discharge  hy  gravitation 
could  not  be  obtained. 

The  System  affords  scientific,  sanitary  sewerage  in  cities  and  districts 
where  gravitation  only  cannot  be  successfully  employed. 

For  particulars  apply  to 


SHONE  COMPANY, 


445  West  46th  Street. 


CHICAGO.   ILL. 


The  Van  Vranken  Automatic 
Sewer  Flush  Tank.  •••    •••    ••• 

Will  discharge  with  the  smallest  feed  stream 
of  any  Tank  in  the  Market,  Does  not  require 
excavation  below  the  bottom  ot  the  sewers  can 
be  used  where  the  depth  of  sewer  is  but 
two   and   one 'half  feet, 

Por  catalogues,  discounts  and  other  particulars,  address 

J.  LELAND  FITZGERALD, 

SCHENECTADY.  NEW    YORK. 


Graptilcal  Sewer  Calculations. 

The  Diagrams  shown  in  the  Chapter  on  "Laws  of 
Flow  in  Sewers"  (pag-es  100  and  108)  can  be  furnished, 
on  extra  hea\w  paper,  with  explanatory  notes,  at  50 
cents  per  copy,  post  paid.  Address, 

GEO.  S.  PIERSON,  Mem.  Am.  Soc,  C.  E., 
Kalamazoo,  Mich. 


Sp6GitlGations  for  Sewers. 

The  Specifications  which  appear  in  this  volume 
have  been  published  in  pamphlet  form,  and  can  be 
obtained   by  addressing-, 

GEO.  S.  PIERSON,   Mem.  Am.  Soc,  C.  E., 
Kalamazoo,  Mich. 

Price  50  Cents  per  Sing-le  Copy,  Post  Paid. 


Elements  ot  Brick  Sewers. 

The  diag-rams  showing-  elements  of  circular  and 
egg-'shaped  Brick  Sewers  which  appear  in  this  volume 
can  be  furnished,  printed  on  heavy  paper,  at  25  cents 
per  copy,  post  paid.     Address, 

GEO.  S.  PIERSON,  Mem.  Am.  Soc,  C.  E., 
Kalamazoo,  Mich. 


ESTABLISHED   1845. 


W,  L  L  E  GURLEY, 

TROY,  N.  Y. 

Largest  Manufacturers  in  America  of  Civil  Engineers'  and 
Surveyors'   Instruments, 


r 

« 

3 

1? 

W 

\ 

a 

m 

nj 

CI 

H 

f2 

T3 

G 

(0 

tj 

U) 

G 

G 

J2 

(Z 

Oi 

j: 

u 

0) 

u 

'A 

•S 

«J 

o 

H* 

(Y. 

o 

r  1 

G 

^  > 
13  « 
>    i-J 


Tl 


O 


2.    B 

0)     Ot> 


11 


to      S. 


Reconnoissance  Transit,  one  vernier  to  limb  sJ^-inch  needle,  with 
vertical  circle  reading  to  5  minutes,  level  on  telescope,  clamp  and 
tangent  to  telescope  axis,  and  tripod  with  extension  legs. 


Our  Latest  Illustrated  Catalogue  and  Price^List  Mailed  on  Application, 


;low. 


Fo 


__  x^v^iWoV^:** 


iiii?Mi'"^^^''  "f  ^'-''VAl  J3HAH,'  Fitlj-. 


A     000  343  406     5 


